I have a starting point and some world build along with a list of custom encounters/Survival checks to use in the coming weeks that this will take. hoping to not railroad my PC's,  this is my first homebrew campaign. I've made one-shots in the past that went well, trying my hat in the full campaign aspect. How do i get my PC's to care for NPCs? I want them to take the plot and create their own, but how do i keep a constant evolving story plot going without railroading them? i have cities to visit, nomads to encounter, dungeons to find and what have you. what is the best way to build without planning too much? that is a great fault of mine, tons of planning and having trouble drawing from improvisation. any advice will help greatly.

Well decide from upfront for their actions, there is a golden rule in DMin and that is expect the unexpected, you can plan things out  when they do things  that elads towards the things you planned, other than that, I recommend going with their actions,

Personally I do only a short preparation  maybe 1 hour of what I want to achieve in this session, and I roll with what my players do,
I tend to overplan and rethink all options if they do things, but leaving it at a solid basis of what you want as a dm and rolling with the players,
and a session being derailed from the plot is not a world ending drama (except if it is ioni your campaign)

and as goes to care for Npc's that all up to the players, you can make the NPC's really important or play them out of their backgrounds/backstories

But the best tip I can give is, Don't plan too much because thats where you want to railroad, and just write down a few sentences that you want to get done that session, and nomatter how they manage to, aslong as you're happy with it, IE:

"There's been a series of grave robberies. The townspeople wouldn't care too much if were just the valuables that were taken, but the bodies are gone too.
The first set of clues points to a quiet teenager who loves spending time at the cemetery being the perpetrator, but he's actually just looking suspicious because he's covering for some crazy man that he has recently befriended and didn't want to get in trouble".

and you play it out in a certain way for them to find out,

my party camped at the cementary and saw a shadowy figure  approaching but noticing them and fleeing
finding out next morning as they heard someone talking about where he was last night and interogated the kid, finding out the truth.

I see a lot of people talking about railroading and sandbox, as though sandbox is the ultimate aim of the game. But honestly, if this is your first campaign, then you want a combination of sandbox and railroad. Railroad is not an inherently bad thing if it's done right. Here are some options that you have:

1) Pure sandbox

This requires vast amounts of time input from the DM before a game begins; unless you have 50 hours of prep time ahead of session 1, then it's probably not viable. People also make the mistake of thinking that Sandbox means 'the PCs can do anything they want.' The truth is that campaigns where the PCs can do anything, and don't have an overwhelmingly strong motivation to follow the storyline, are not generally satisfying.

2) Pure railroad

You design only specific places, encounters and NPCs and the PCs basically have to follow your lead or there's nothing for them to do. The truth is, that sandbox usually also has to work this way, or it's just bumping from random event to random combat to sitting not knowing what to do in the tavern where the PCs met. A one-shot game generally has to work as a railroad.

3) Time-space matrix

This is the biggest time investment, but it gives the most satisfying end result. It's also very manageable for a new DM, unlike Pure Sandbox which is unmanageable even for most veteran DMs. Here's how to do it:

• Design a starting area. This area should include a village or other 'safe' space where the players can interact with NPCs. The PCs will start here, or will start on the road towards it and have an inciting incident (if they are new players, the incident should teach them how combat works too).
• Think of the key issue in the area - just choose one. This could be: a gang of bandits are causing trouble, a hag has been kidnapping children etc. Make it something that revolves around one key enemy, but also their organisation/group/allies. This means you can have multiple encounters based around it.
• Think of things that the bad guys will have done in the area, and create 3 places around the village that the PCs can go to where they'll encounter these. In each one, include something that links to the other two - this means that the PCs get a choice after going there on whether to go back to the village, or straight on to more adventure.
•  The PCs must complete the first 3 elements before they will find out about/be able to go to the 'boss' location.
• Create other NPCs connected to the bad guys (usually at least 1 'ally' who is working for the baddies, and others all connected to the threat: maybe the mayor has been paid off, the blacksmith won't work for the PCs because his daughter has been taken by the hag and he wrongly thinks to appease her) 
• Design a more complex area where the boss element dwells. The PCs could technically stumble into it.
• Now draw up a calendar, and first put in a 'final encounter' that occurs about 1 week after the PCs arrive at the village. This will be a major incident, like the bandits attack or the hag sacrifices the children.
• Now look at all your key NPCs. Write down where they are going, and what they are doing on each day (brief notes)
• Create 1 significant event that takes place every other day, which is visible if the PCs are in the right location, or found clues to get them there. These events happen whether they are there or not.
• Run the game: events happen at the times you dictated, but modify depending on PC interactions.

Here's a worked example. I'll time how long it takes me to write this:

• The level 1 PCs start on a road and are attacked by a small number of evil fey (CR1/8) in service to Martha the Green Hag. They hopefully rescue a child from the fey who had been kidnapped having wandered away.
• The PCs arrive at a local village. There is a bad atmosphere, no travellers. No children around. If they saved the child in the opening encounter, the villagers desperately ask the PCs to help them. They don't know where the hag is based.
• There are three areas that might be useful:
  
  • An abandoned farm, where strange noises have been heard by night and all the crops failed. If the PCs go there, they'll discover a ritual symbol in the basement. The former owners were in league with the hag, but she ate them. There are some more of the bad fey there. The PCs might find a star map. The star map takes an astronomer in the village 2 days to decipher. The star map will show them what the hag needs to do.
  • A dark cave where an Owlbear dwells. The owlbear killed the last adventurers who tried to help the village. The owlbear isn't connected to the hag, other than that it hates her for blinding it in one eye and wants to eat her. Clever PCs could speak to it with magic and try to gain it as an ally to unleash later. Otherwise, the PCs can find the journal of a dead adventurer in its lair that shows that the hag wants to permanently become an elf, but can only do so with sacrificing children - but they all have to be sac'd at once, on a particular night. The PCs can find out when the sac will take place.
  • A laboratory where a mad inventor works. There are some modrons helping him. The inventor has created the contraption for the hag, and knows that it needed special tracks to move. This will indicate to the PCs where the sacrifice will take place - a circle of standing stones.
• Other NPCs in the village:
  
  • The town elder has been promised youth by the hag, and will get in the PC's way. This can be misinformation, but in his home there is info on what the hag is doing. He will summon his guards to fight if need be.
  • A young orphan girl with sorcerer abilities wants her sister back from the hag. She can provide useful info on 2 of the 3 locations
  • A retired, one-legged adventurer wastes the PCs time with false leads
  • A tricksy genasi feigns romantic interest in order to rob the PCs
  • A bad-at-singing bard hopes to pass info to the hag in order to be spared. If successful, there's an ambush encounter
• The hag dwells in a ruined hunting lodge, surrounded by Blight infested gardens, about a day's walk from the village. The children are being kept here.
• The hag will do her ritual in 1 week's time, if the PCs have done nothing to stop her. It takes place at a circle of standing stones that mirror the star map found at the farm. If the PCs are there early, they can set a trap. If they kill her in her lair before that, there's no ritual.
• Each NPC then needs a daily schedule of where they'll be and what they do. For example, the orphan girl has to work in the bakery by day, but by night she's often sitting alone in a garden. On days 2 and 5, she goes to visit her elderly aunt who lives outside the village. On day 7 she tries to stop the hag herself.
• Significant events:
  • Day 2, a fey enemy turns up and tries to kidnap another child between 10pm and 2am. Observant or patrolling PCs in the village will encounter this and may or may not prevent it.
  • Day 4, if it hasn't been dealt with the owlbear attacks a caravan coming from the other direction
  • Day 6, if the town elder is still active he sends a rogue accomplice to destroy the PC's gear at night, in the hope that this will stop them. He then goes to meet with the hag at the abandoned farm. 

This whole design took me 13 minutes and I had fun doing it :) It provides a complete level 1-2 adventure and I can flesh out the areas as much as I like. The end result of the 'week' entirely depends on what the PCs have done. The clues they find should be quite blatant - you don't want them to get lost in not knowing what to do!

I recommend the time-matrix style, it's fun to run for the DM too as it feels like the world is breathing without your help once it starts going. 

As an addition, in terms of not railroading them - stop building cities and far off places. To begin with, keep it small and local. You can know the names of a couple of nearby cities, but think small scale so that you design things for the PCs when they are going there.

To expand the game after the hag, the hag got the evil plans from the other 3 hags in her coven. The coven is spread out, and occupy positions of power in a nearby town. A village is suitable for levels 1-3, a town for 4-7, and cities beyond that if the campaign is still running (it probably takes a year of bi-weekly games to get from level 1 to level 7, there's no need to be planning for that right at the off).

Don't over build - see what the PCs are interested in after the first few games, but make those games shine with detail.

Gonna just drop this here for you to peruse at your leisure. Sly Flourish - Thinking Two Horizons Out

You can design a linear plot with checkpoints to be accomplished to defeat your BBE in whatever form it will take. Not allowing your players to deviate from that linear design is, in effect, removing their player agency and railroading them. Puzzles can be the easiest way to frame this. If you design a dungeon room where the correct solution of a puzzle as the only way for your PCs to get out, you are forcing them to use your solution. If, instead, you allow them to use their own solution on the same room you are valuing their choices and thus not railroading. Drop plot hooks and carrots to coax them toward the path when they inevitably veer off from it, but ultimately let their choice stand.

My 2cp on prepping your world - focus on a list of NPC names, rumors, secrets and the like. When the PCs wind up in a tavern or on a caravan, and you want to drop them a plot hook, that plot hook has to come from somewhere. Local gossip and little details of the already built cities / towns can make them feel bigger than they actually are. If your players are anything like mine are, they will more than likely make "friends" with more than just the BBE. Take good notes, and let the players feed you with plot ideas as they try to figure out how or why the BBE did the latest thing.