A lot of games talk about letting you play anyway you want to, but Far Cry 5 embraces the ethos more than most- making almost any perk available at the start of the game. Which perks work best will depend on your playstyle, but here are a few all-around good perks.
While you can certainly complete the game with just two weapon slots, more weapons at hand gives more tactical options in any scenario. Whether you want to keep a spare rocket launcher for vehicle encounters, a bow for hunting, or even a low-level sniper rifle for when your .50 cal rifle runs out of ammo, you'll never find yourself thinking that you have too*many available weapons to choose from.
This one point perk isn't useful everywhere, but it will pay for itself many times over in granting you access to Prepper Stashs and other secret hideyholes. Like the Parachute and Wingsuit which follow, Grapple is pretty much indispensable for seeing the whole of the game.
This probably shouldn't be your first pick, but if you do like vehicles, it's hard to beat. Even if you don't like vehicles, this perk can make the game's many vehicle based missions into a cakewalks, and can help with some stunts and achievements. Plus, it means you'll never have to listen to that 'helicopter in danger whooping alarm' for more than five seconds in a row, ever again.
After lone-wolfing it through earlier Far Cry games, having a sidekick tagging along can seem a little irritating, to say nothing of two. But the Far Cry 5 companions are pretty good at staying out of your way, and both their combat abilities and special abilities can be very useful for your struggle. In particular, you can take over many outposts with companions alone, making it easy to get your hands on that $1000 dollar stealth bonus. Companions can also resurrect you when you fall (some even have special abilities just for that sot of thing), making an extra companion almost like an extra life,
More stuff means more options. The larger inventory space also means that, while hunting, you don't have to rush back to a merchant every two minutes in order to offload skins.
Harvest Master/Fisher King
Neither of these is going to help you clear an outpost, shoot down a plane, or unbrainwash a comrade, but they're both good for making money in Hope County's meat-based economy, and both will help you reach achievements that are nigh impossible otherwise.