Noob questions

How long (playing time) does it usually take for a player (starting from new server) to reach Mid Game (1kk power). I've been playing for a while and I'm usually ranked about 25th on H2H and public events (about 630k power). I'm using Celebi, Giranita and Steelix. Do you guys believe that is a solid team I should keep leveling up? I also have Zapdos and Mew, but I have not upgraded them.

I've been reading posts and currently I have about 21k diamonds saved for an event. What Pokémon should I aim for?

Thank you mates

xoxo