i recently started my first campaign, i obviously don't have the money to get proper stuff so i mostly just do a wole lot of improv, now this is great and all until i finally have a set story that i know my PC's will want to do (or so i thought), but they then manage to find loopholes to almost completely skip parts of the story and get all the rewards, is there any way i can stop this from happening?

Quote from Shadytheshadiest >>

i recently started my first campaign, i obviously don't have the money to get proper stuff so i mostly just do a wole lot of improv, now this is great and all until i finally have a set story that i know my PC's will want to do (or so i thought), but they then manage to find loopholes to almost completely skip parts of the story and get all the rewards, is there any way i can stop this from happening?

 
Welcome to the hobby.  I find that the best way to offer advice is by simply coming up with some questions.  Answer them and then you'll know what you should do.

Do you think if your players do something clever and find a way to solve a problem you presented by avoiding it entirely, should they be rewarded for it?  

What is the story of a D&D campaign?  Is it what you write-prepare, or is it what the players do and what happens?

Do you want to stop players from cleverly circumventing challenges you place before them?

If you want an opinion, which I think you should take with a grain of salt is that the point of being a DM and really the entire exercise of running a campaign is very specifically to do it your way, to find your own voice.

That said, my personal take is that an RPG campaign isn't about the story I write, its about what happens, what the players do, what they think, its about the direction they choose to go.  The story is just what I prepare, but when I prepare a game session, if I really want to be prepared, I don't write deterministic stories about what I expect to happen.  I write stories based on what would happen if the players did not intervene at all.  They don't intervene, how does the story play out without them, what happens?  What do the villains do?  What consequences are there?  Then I simply adjust the story based on what actually happens, how do the villains respond to the players intervention, what do they plan to do next.

Essentially, I write the story, but I write it without assumptions about what will happen when the players arrive, I let that part emerge in the course of play.  

This is my personal way when it comes to plots and villains.

The other thing I do is simply prepare the world.  Its a place, that has people and unique locations, life goes on with or without the players, I define this place so that when they go north or  south , I'm just as ready as if they went east or west.  Typically for new players I recommend either a very small setting of your own creation or a purchased setting.

1st rule of DMing: Make it yours.

2nd Rule of DMing: Players will never do whatever it is you think they will do.

1st Corollary to Rule 2: This includes even when you think up a dozen different things that they could do.

2nd Corollary to Rule 2: When you don' t think they will do anything, they will do something even more unexpected.

3rd Rule of DMing: Thou Shalt Not Railroad.

1st Corollary to Rule 3: The game isn' t the story of your characters, it is the story of their characters.

2nd Corollary to Rule 3: Let the players decide how they ended up together to get things started. Give them the time and the place, and see what they do.

smort

Quote from AEDorsay >>

1st rule of DMing: Make it yours.

2nd Rule of DMing: Players will never do whatever it is you think they will do.

1st Corollary to Rule 2: This includes even when you think up a dozen different things that they could do.

2nd Corollary to Rule 2: When you don' t think they will do anything, they will do something even more unexpected.

3rd Rule of DMing: Thou Shalt Not Railroad.

1st Corollary to Rule 3: The game isn' t the story of your characters, it is the story of their characters.

2nd Corollary to Rule 3: Let the players decide how they ended up together to get things started. Give them the time and the place, and see what they do.

 Some of the best DMing advice I've seen, and I could not agree more. 

To the original poster of this thread, I'll also add a bit of advice on how to plan: 

Don't bother writing up your desired story in exquisite and minute detail--as has been stated: your players will rarely choose the expected path. If you're planning your own adventures, just use an outline format. Also, the OneNote app (or similar notetaking apps) are of immense help in this. And again, as has also already been said, just accept the fact that you will plan out entire encounters and scenes that do not happen.

In the end, we can all offer advice, but DMing is an art form. It takes time, patience, and a love for the role. Relax into it and have fun. :-) 

I advise you to write only what has happened, not what will happen.

EG, instead of your notes saying "the party finds a locked door, so they will pick the lock", instead say "The enemy they pursue has locked the door, and they will need to work out how to get past it".

The first means you might make plans for their picking the lock, which they throw out of the window by scaling the wall, breaking the door, or wildshaping into a fly to get through the keyhole. The second means that however they do it, it does not change the past.

Basically, write everything right up until the players take their agency, and start playing. After that, you need to decide what happens on the fly (your job as the DM) based on the world things are happening, and the past.

Another example is combats - don't write combats, write encounters. They meet a wolf who's hungry and afraid of humanoids. That leaves you motives if they say "I cast speak with animals" or something, whereas "They fight a wolf" is you deciding things for them, which will lead to disappointment.