I've started playing mtg on a low level last year, this is one of my first times trying to make a real deck. There should be a lot of cards in the deck that shouldn't be and a lot of cards that should be in the deck but aren't. So I would really appreciate advice.
Also, I don't have an unlimmited budget. I'd say the deck should have a total price of at most $150, and every card should be at most $10, unless it's really good for my deck, in which case the max should be $15.
I would highly recommend stretching your budget for just one card. the card that belongs in every mayael deck: scroll rack.
The card is so amazing in mayael it's worth just not getting 2 other 10$ cards. maybe you could find a heavy played one for $18-22.
other highly recommended utility cards (most of which are cheap): bloom tender generates 3 mana when mayael is out. aura shards - repeatable artifact/enchantment removal Return to Dust - good removal in general, but also can get rid of things that are indestructable (darksteel/blightsteel colossus, darksteel forge, etc) Krosan Grip - stops infinite combos. lignify - turns generals and really threatnening creatures into worthless weenies. Faith's Fetters - I don't care about the life gain, it's good because it can target anything.
note about tokens:
Some might disagree, but I think some token generation is very helpful in a mayael deck because it gives you random dorks to sac if someone forces you to sac a creature. I run Awakening Zone. it's so great with this deck because you've got dudes to sac and chump block when you need to (if they have a creature with deathtouch, for example) and extra mana for hardcasting stuff. I also run living hive, kher keep, Rampaging Baloths, ant queen, Wurmcoil Engine and Artifact Mutation. I also run ashnod's altar because I'm running tokens, but also because it's a quick and dirty way to prevent your creatures from getting stolen. it sucks that you have to sac them to prevent it, but I'd rather it be in my graveyard than on the other side of the table.
here's some cards you're running that I ended up taking out of my deck for something else. note that I'm not saying your choices suck, but just showing you what didn't work well for me. these cards might work way better for you than they did for me:
Elvish Piper - gets killed too fast
Hydra Omnivore - no trample
Mossbridge Troll - i found it boring unless I was going to combo, but I don't really like the combo either.
Pelakka Wurm - good, but not good enough to my eyes.
Ingot Chewer - not P5 or greater and I just think artifact mutation is way more fun and funny.
wooly thoctar a vanilla 5/4 always felt like a waste ot me in EDH.
deathrender - this didn't quite make the cut because I want creatures in my library more than in my hand.
I think Triumph of the Hordes might be fun/funny but haven't tested it yet. also burning wish would be interesting because you could run some sweeps and spot removal outside of the game and not take up as many deck slots.
I wish I had an up-to-date list of my deck. I think you could scan through it and find a lot of cards you may not have come across that are ever so slightly more effective than some of your choices. here's an old list I don't really play anymore, but it's worth a look:
I think mayael's weaknesses are token decks and decks that force you to sac creatures. I run some tokens to deal with forced sacing and aether flash to deal with really fast token decks. I'm still a bit weak vs. token decks, but only when they are pretty fast and aggressive. I've been thinking about running crawlspaceas well. my deck is also just a tiny bit weak against flying themed decks. I have some flying but not enough to keep up with a deck that is mostly flying. I run gravity well for this reason and for the reason that i think it's a funny card to lay on the table. no one ever expects it. sometimes I take it out because it's not all that great, but I just like it. I have about 4 "because I just like it" cards in my deck. retaliator griffin was one of those cards for a while, but I felt guilty not having a higher amount of power 5 or greater creatures so I took him out.