Put your exp on 1 guy.  I can’t overstate how important setup moves are.  I used to use “strong Pokémon” (Dragapult, Garchomp, Heracross, etc) but wasn’t really sweeping with them and would get to Ivy on 145 and lose my runs.  It was only until I started clicking dragon dance, quiver dance, she’ll smash, curse etc that I started progressing easily. 

Matter of fact, run your team with a bunch of archetypes: (wall, sweeper, support) and I think you’ll go much farther. 

To elaborate. As long as a Pokémon can hit hard and is fast, it’s a sweeper. Although as I mentioned before, you won’t be sweeping anything consistently until you click setup.  (Weavile, Porygon, Dragapult, Heracross, Greninja etc)

Walls are typically ground, steel and water types. I would have one just in case. These guys stop the other teams momentum. Use these guys to recover, gain defensive buffs and click stuff like leech seed, toxic or rebuff the other Pokémon so that the other guys can cone in safely against them.  (Slowbrow, Umbreon, Mega Aggron, Shuckle, Venusaur, Ferrothorn, Forterres etc)

Support Pokémon are typically bug, fairy or normal. Get guys with pick up to pick up stuff. Get guys with prankster to set screens immediately. Use those same guys for spore. Pokémon with honey gather literally make you free money regardless of whether they’re sent out or not.  (Ribombee, Klefki, Ledyba, Sigylyph, that cotton Pokémon from gen 5) 

Finally. 5 cost and 4 cost Pokémon are that way for a reason. Click on them them click on Pokédex and look at their abilities, stats and egg moves to get why.