Hello again I will divide this up into basic and specific tups
Basic: in the opal ward the building that you get your starter in there are rebattleable trainers and they scale with your badge level great for grinding levels
Catch a few pokemon that you will train so you can swap them out with some of your other team members for hard fights
Specific
Male meowstic is a setup mon great for boosting your team's defense with his ability prankster it allows all status moves to gain priority so teach him light screen reflect psychic and thunder wave. Use an ability capsule on him
Gyarados great pokemon has access to dragon dance waterfall earthquake and bounce. Although he is outclassed by azumarill
Which you can get if you are lucky with mystery egg or between agate city and glass factory is another location for azumarill huge power makes it hit like a freight train.
Roserade doesn't learn a bunch of poison moves so you are going to have to teach it sludge bomb. Otherwise a great pokemon
Blaziken is one of the best suicide mons it should be taught hi jump kick flare blitz brave bird and swords dance.
Kricketot is great early game but later should be replaced by a stronger pokemon like excadrill who is fast and strong.
And zigzagoon should later be replaced by a pokemon of your choice like magnezone ampharos or any pokemon of your choicw