About half of the wildcards you'll need to boost, those are the most random ones. Like 52 kills in a round, 4 helicopter roadkills in a round, 50 boat roadkills (global). A handful of wildcards you can get yourself but most will probably require boosting.
I myself boosted the grenade launcher efficiency trophy though it's not terrible difficult, plus I'm gonna have to boost the naval warfare patches because I don't find the boats that great in combat. Helicopter trophies are tricky at first but just keep trying and you can get enough for the patches. Just basically anything in the game you have some trouble with (maybe boats, helicopters, emplacements) you should boost, and most of the wildcards.
You usually wait until the early morning when there's less people playing. With a bit of luck you can get an empty or almost empty room and wait for it to clear it. Minimun players is 4 people so you need at least 3 other to boost. It's mostly luck since sometimes people will join your room and ruin it but sometimes you can hold a room all to yourself.