>>47393060Just keep your team levels close.
Most trainers from heron will use your highest level mon to scale their teams. There's a mild benefit to being level 100, in that some pokemon will overlevel your highest by one or two, but generally, I find keeping it easier to add new teammates to be the best strategy. This is especially true if you're trying to make relative shitmons work in ebin that aren't cherrypicked for whatever trainer.
North of Dubs island, you'll find the Grindhaus Ranch. You can effortlessly grind EVs or EXP there, getting there should be a priority, as postgame generally relies on you having well trained pokemon, not just high level ones.
Generally speaking, support is your friend. Spread paralysis and burns, set up stealth rock or spikes, catch switches with Rock Tomb. Just mashing attack won't work unless you're using the best pokemon Clover has to offer.
Also, note that there's no real order to the Ebin gyms, besides the last one which is always last. Do them in whatever order you want, explore first, pick up pokemon geared for the gyms specifically.