Yeah, if you swap into a Linker, Napalm would be a good option. R.I.P. is not that good when using Joint Penalty.
About gearing progression: You should equip yourself with HG Leather Berthas equipment (eaglestar, kaulas etc…) until Level 350. As for Stats, STR/DEX/Crit Rate are the ones you want.
At level 350 you should try getting Fietas Equipment and a Primus Raffye Pistol/Masinios Pystol. I’ve used Fietas +11 and a Primus Raffye Pistol +16 until I got my Ichored Velcoffer.
As assassin you’ll need a good dagger too, so I recommend sticking with Raffye until you get Velcoffer Weapons. Raffyes/Masinios are cheaper and you need less bless gems/silver to trans/upgrade.
About acessories, the new Irredian Abyss Set is a very good option and isn’t that expensive. I’d wait till level 380 and save some money to get it. Until then, you should get a Max Petamion and some generic bracelets.
There isn’t much to talk about it, but if you have any question about what I said, just ask!
Masinios - First Game Raid: where you get Masinios Weapons Recipes and Fietas Leather Set Recipes
Velcoffer - End Game Raid: the best Legendary equipment come from this raid. Your objective should be gearing yourself so you can start running this raid.