I am dm'ing my first campaign for a group of friends. It is a homebrew world and I have created a cult that is going to be attempting to bring the main villain to the prime material plane. However, I feel like I am struggling with giving up too much to the players too soon.

I introduced the idea of the cult during the last 2 sessions. The party worked through the Halloween Encounter The Haunted Cornfield . I used this since the cult is associated with Asmodeus and I thought the use of imps could be a nice segway to get the party thinking about devils and such. After they completed the Haunted Cornfield, they began asking around the town, Grasshire, to see if anyone had seen any other types of devil related activity going on. So I had one of the townsfolk suggest that they go to the local Tavern/Inn and ask the inn-keep if she had heard any rumors from any traveling merchants or adventurers. Since they still had some of the adventuring day left at the time, they checked into the inn and decided to check out a couple of shops. The next morning they questioned the inn-keep and she told them of a traveling merchant that frequents the area, once was traveling between towns and got lost. Around sundown he came across some ruins, there he wandered for a while before stumbling into a group of hooded figures circling a fire with 3 small creatures flying around and a large "monster" appearing in the fire. While attempting to leave without being noticed, he stepped on some branches which alerted the hooded figures to his presence. He immediately began running and didn't stop until he made his way into town. After the inn-keep told her story the party went to check out a shop that was closed the evening before. When the party returned to the inn, they were met with a large crowd surrounding the inn. One of the townsfolk said that someone was found dead inside. The party was able to convince the crowd of people to go back their homes and then persuaded the mayor who was guarding the door, to let them in. The mayor led them to the inn-keep's body which was nailed to the wall of the storage room and a large unicursal hexagram was painted in blood above the body. The party then explained what they saw at the haunted farm and became a set of potential suspects of the murder. as the party left the inn, one of the characters noticed a single raven perched atop the building across from the inn. The party is currently on their way to find the ruins from the inn-keeps story in an attempt to find evidence of the potential cult to clear their names. 

I am worried that I gave too much too soon already and I honestly have no real idea of what to do when the party reaches the ruins. I have considered them simply finding an old encampment that has been abandoned with minor things like bloody rags, some candles that have burned themselves out, and journal with a unicursal hexagram on the cover with its pages ripped out. However, I feel like that's somewhat of a cop out. 

I know that this is a long post but if anyone has any suggestions on how to handle this, I would greatly appreciate it. 

Roll up some cultists for them to encounter, maybe have them in the middle of a ritual, or having just finished a ritual. Maybe one is a decent spellcaster to give the encounter some edge without making it to hard. With a cult plot you possibly have an endless amount of baddies to throw at the party. 

Piggy backing off of csheet's idea:

They find their way toward the ritual site, running into various cultists running toward them, not at them. They're scared, if the players try to stop them, it's a fight with the cultist trying to flee. Have one cultist, the spell caster mentioned, freak out when he sees the players and try to kill them, but play him off as completely insane. Then have the players finally make it to the ritual site only to witness:

A giant demon, standing in a ritual fire, swipes an arm, decapitating a half-dozen cultists in one blow, grabs one up and eats it. Then storms off in the opposite direction of the group. They can find the "proof" they need for their innocence and you've now got something that could make for a good story.

Thanks for the ideas guys. I think that I will have a group of cultists led by an evil archmage in the ruins, that are attempting to commune with a pit fiend to receive some instruction on what they need to do to begin the process of allowing Mallum(big baddie) to ascend from the nine hells. This will allow the party an opportunity to listen in and start to understand the cults motivations if they take the not so murder hobo route. If the party is discovered by the cultists prior to any combat begins, I can have the archmage and 2 cult fanatics cast darkness, allowing the cultists to make a clean getaway. I can also use the darkness after a few rounds of combat too, if it comes down to combat. After the darkness spell lifts, the party can gather evidence from what is left behind. 

What do you guys think?

That is a solid idea, if you party actually eavesdrops on the baddies I will be jealous as my group is always rush in and then panic when they run into a situation they didn't anticipate lol. 

The best way I have found to introduce your PCs to a cult is by dropping seeds (clues) like a ritual interrupted or having a cultist confront the party in secret. I am introducing my players to a cultist I have drawn on their backstories for the perfect opportunity for the cultist to pick holes in their backstories and create a drift of distrust within the party. I know that 2 party members may have heard of the cult but its inevitability comes down to dice rolls. But using the player's back stories to draw on inspiration makes it feel authentic to the players and not something thought up on the fly.