Well, this is my first deck I'd like some suggestions on how to improve it.

http://deckbox.org/sets/321064

Ok, few things to note:

I own none of these cards; my budget is $60 - 80, the lower the better!
Format doesn't concern me(Legacy, Vintage, Standard, Modern whatever) I play casually with a group of friends and have no intentions of playing competitively.

This began as a changeling buff to eventually "use changelings to bring out massive creatures".

The Didgeridoo helps me bring out changelings and by playing Cryptic Gate I can easily summon the massive monsters. The tutors help me get whatever I need.

I've also thrown in a few buffs for the changelings and the Kilnmouth Dragon has massive buffing potential.

It's currently all over the place, some feedback/help would be much appreciated, thanks!

Just off of initial observations, it seems a little slow. Cryptic gateway is 5 Mana, and you have 0 ramp.
If you like the concept, you could go GW, run elves and Mirror entity. However if you are running elves you could just hypothetically ramp into Emrakul (Or something). Not really sure what to suggest though if you are going to be on a budget.

Yes, it is pretty slow and that's also one of it's problems.

I like the idea of running GW elves but my problem with that is that it may be overly reliant on Mirror Entity, as in if I don't get one within the first few turns the match may be decided for me. Of course, I'll still have the elves but for them to win a match alone might prove difficult.

To be honest, if the budget is that much of an issue I can quite easily get rid of the Progenitus and replace it with cheaper creatures.

I like the idea of bringing out massive creatures with Cryptic Gate, as they don't even need to be restricted to color!

However, if anyone has suggestions for the Changeling buff side of this deck that'd be great too! I don't think it's a good idea to keep both strategies in, or maybe it is. Thank you!

I've just realized that if I run a G I can throw in some Descendents' Path and try to pull off some big creatures that way.

Would that be a good idea?

On average Descendants' Path is going to under perform and will, in most cases, end up putting something you might've needed (land, removal, etc) on the bottom of your library. From experience trying to use it competitively, it's just not worth it.

While it's true that Descendents' Path is probably too slow, just in terms of basic probability it makes you no less likely to draw enchantments or sorceries than not playing it. If all the card did was take the top card of your deck and put it on the bottom, without revealing it or allowing you to play it, you wouldn't think that it was depriving you of lands or whatever; it would just be a reordering of your deck, and if your deck is properly shuffled it wouldn't matter. It wouldn't increase or decrease your odds of drawing anything. The fact that it reveals the card and can play creatures for free doesn't change your odds either.

That being said, your odds of drawing a creature in a typical deck would be a little under 1 in 3. If you play Descendents' Path on turn 3, you're probably only going to get a creature every 3 turns, so maybe one on turn 5, one on turn 9, one on turn 10... Potentially powerful in longer games, but also pretty unreliable. I was thinking the other day of a hypothetical deck with massive land ramp followed by 4 Descendants' Paths. It was an entertaining idea, and could theoretically be extremely powerful, but it might also probably be too slow or improbable at getting started in the first place. Draining your deck of lands would increase your odds of drawing creatures and more Paths though. I'd be interested in doing the math on that deck... later.

But yeah, sorry I got sidetracked. No, in general throwing in a Descendants' Path is not going to automatically make your deck an unstoppable monster generator. Primal Surge could though. But as far as this deck is concerned, it's already way too slow, so that wouldn't help you at all with its high cost - you'll already have lost by then. Maybe add some cheaper cards that help you draw more land or extra cards, and some removal so you can hope to make it to later in the game.

You have Progenitus in there with NO WAY to cast it. Is it in there just for a chance at re-shuffling? If that is the case, go with an Eldrazi that does that since you can cast it in multiple ways. Emrakul comes to mind instantly for a bonus kick.