1. One place you can take to ask about teambuilding would be the teambuilding help thread, linked
here. You can also do some asking on the Battle Spot room on Pokémon Showdown or the Discord channel, where people are on fairly often and usually wouldn't mind helping out.
2. Unfortunately, current Battle Spot rules require all Pokémon be bred or caught in gen 6 and 7 games only (XY, ORAS, SM, USUM), so unfortunately you can't use Refresh Mega Pidgeot since it's only available as a gen 3 transfer. On top of that, Mega Pidgeot is a very niche mega evolution, since it often doesn't have enough power to do what it wants, has a somewhat lacking movepool, and faces heavy competition for a team's mega slot from things like Mega Salamence, Mega Blaziken, Mega Charizard X and Y, and more. However, if you still want to build around it, I would say it is possible, but it'd take a lot of support to work. Feel free to ask and experiment with it though.
Hope that answered your questions, since I'm not the greatest at that kind of stuff.