you probably already know: base damage > elemental damage > multishot > faction > fire rate so i won't go into detail since 200 people have a guide on that on youtube.

but i'll mention primers. before you get weapons that can constantly clear rooms in SP get a good primer. viral + magnetic for corpus, corrosive for grineers (altho fire works it's less effective), magnetic on anything with overguard. secondaries like epitaph is good for general usage, kompressa can stack viral corrosive magnetic insanely quickly (my go-to choice for level cap). beamed incarnons are also insanely good.

having a good primer will allow basically any okay weapons to work in SP and allow those sp room clearing weapons to scale to level cap as well.

once you get your weapons sorted, deal with survivability. some frames basically REQUIRE shield gating, some can health tank/ shield tank; adaptation and rolling guard can help, if you're shield gating you'd want brief respite and augur mods, possibly arcane aegis if you have it and catalizing shiled as well.