Team building

[Kataklyst]

Hey guys I really want to get into competetive pokemon battling but I kind of suck at building a good team. So if anyone could help me I'd greatly appreciate it. Here are some pokemon I would prefer on my team but obviosly I can't have them all. 
Milotic
Metagross
Charizard
Hydreigon
Lucario
Banette
Dratini
Froslass
Cherrim
Porygon-Z
Furfrou
Mewtwo
Greninja


Thanks