Valve has added a new collection of tutorials for Dota 2 to help newer players with movement, general tactics, and hard combat. The new system will teach you everything step by step, at which point it'll allow you to take on a pared down selection of the game's cast, as you learn each character's strengths and weaknesses.
If you've ever wanted to learn how a MOBA works, the free Dota 2 is a great start. Almost 10 years ago I got my start with the original Dota, and I ended up applying that knowledge to pretty much every MOBA out there right now.
You will have to give it some extra effort if you want to learn the meta-game and the ins and outs of each character as it pertains to match-ups and team fights, but it's a start.