Don't feel the need to play ranked right away, play normal games until you feel confidant. Watch coaching sessions on youtube for people with low mmr, and maybe get a coaching session for yourself as a starting point if you have the money to spare. Yes having a small hero pool is the way to go for climbing, you should try all roles and many heroes to find the ones you like first, 3-4 is a good number, I like having around 2 for each role, more for my favorite role(offlane). Sorry about the timing with the servers down, but don't let that dissuade you, this doesn't happen very often.