New to Deck Building

I've never built my own decks until recently, and I would appreciate any feedback you are willing to offer. I'm not looking to get into tournaments or anything like that, just some fun with friends. I've built most of my decks around a common theme with at least one "high" card (high mana cost and high P/T).

Fire Breath I tried centering around overwhelming damage with as low a mana cost as possible.

Midnight Change is a wolf/werewolf deck that I put together more as a theme than with any specific purpose, although it seems to have a balance of mana cost vs damage.

Bloodlust I created with the idea of having as much lifelink as possible while also dealing some powerful damage through Deathtouch.

Dark Forest is a mix of gaining a little life, having a lot of mana, creatures that are already powerful, and creatures that can become powerful.

Deathtouch was centered around having as many creatures with Deathtouch as possible, and the creatures that don't have Deathtouch have either a high power or a high toughness.

Hell Rising I built around bringing creatures back from the graveyard coupled with the damage from my "high" cards.

River Bend I tried going for flying creatures on the blue side, low mana cost and complimenting creatures on the white side, and some counter spells. I'm pretty limited on my blue and white cards, so this deck could probably be a lot better.

I don't really have anyone to play with, so I haven't been able to really try them out to see how they do in real time. I would appreciate any advice you can give me on how the decks may play out during a game, if my mana costs are too high, if I need to think differently when I build my decks, if I'm just an idiot when it comes to building decks, and anything else you think would be helpful. I'm not worried about having to buy cards, so if you have any suggestions on cards the can help any of my decks feel free to list them.

Thank you for your time and your feedback/advice.