What's good armour to use for an assassin on this game? I can't get mods as I'm on xbox, thanks!

chinese stealth suit, assassian suit from DM, theres another steal suit in OWB. any light armor would fit the assassian build.

Also it depends if you are an assassin that prefers to remain hidden or hide in plain sight

This ^. In addition I will keep pre war business clothes, and wastelander clothes for blending in. Depending on the target some power ganger gear, legion clothes, NCR armor, etc. can come in handy. Example: Best clothes for assassinating Caesar.... Legion Vet armor .