DotA 2 is like a good game of chess that has done acid and decided to invite all of its 'friends' over to brutalize and torment the other team. However, instead of tormenting the other team these 'friends' just decide to rail on one another until each 'friend' has to quietly put themselves into offline mode before playing any game on steam.
Honestly though, contrary to popular opinion DotA is a very fun game. It is just not a fun game for stupid people or people that are not willing to take some time to learn the game. This game will not spoonfeed you on how to play, nor will it easily allow you to catch up if you make mistakes. Like in the real world if you make mistakes in battle you will suffer.
A few tips:
Try to keep a level head, and bonus points for a positive attitude. Your team will appreciate it a lot, and they will be more willing to work with you.
Pay attention to the map, your surroundings, and your enemies items.
Read your abilities carefully, read the patch notes, read the items abilities.
Practice heroes in demo mode (this is different from bot practice or private lobby.)
Get yourself a mic. Effective communication is one of your biggest utilities.
If a hero that is in your lane goes missing call missing immediately. Better safe than sorry.
Buy wards. Wards might typically be a supports 'job', but they will save your life and get you kills, which will easily make up for the gold cost. Also, your team will appreciate you that much more, which will result in them being much more likely to try to help you out and listen to you.
Use your scan. I find that this tool is way overlooked. At least in my bracket. It's up every 5 minutes, and it can only help (if not to tell you where someone is; it will tell you where they are not.)
Nobody is good at DotA. There is always someone much better than you are. So do your best and try not to talk trash.
Treat this as a chance to develop team communication skills
Deny creeps as much as you can, but not at the sacrifice of missing a last hit.
Buy smoke before a gank or a Rosh kill. They are a cheap invaluable tool.
Verbally tell whomever you are around if you are planning on leaving them or TPing out.
Experiment with different items when you are fighting different types of heroes.
I say this last one with caution because it can hinder your ability to play the game normally, but try Turbo when you first start out. It will allow you to learn heroes more quickly.
Okay, actually this is my last point. Try to have fun. It is just a game.
Your mostly non-toxic Dota friend,
Havoc Octavian Teslasmith