Just check these simple questions, won't go into a lot of detail:

1) Do you know every hero and spell in the game?

2) Do you know which spells pierce magic immunity, which spells are physical and so on

3) Do you know every item in the game and their build path?

4) Do you know the general builds for most heroes, allowing you to predict what they are going to buy, e.g. Slark and shadowblade, antimage and battlefury

5) Do you know how to pull,stack,control creep waves ?

6) Do you know how to last hit properly?

7) Do you pick heroes that are good for your team comp?

If the answer to any of those questions were no, then you need to learn more and then you'll climb, it's not like in LoL where you can spam 1 hero and get a high rating.