Fleet wise, executrix plus geos and hound’s tooth will carry you until you get a sustainable GET2 income to go for either Malevolence or Negotiator (but trying to stay competitive in fleet is generally a little easier than squad). Short term, geos are pretty good at g12, and if you Relic GBA and maybe Spy, you will dominate the Wat shard mission and be pretty competitive against the Nexu as well.
Since we have (thus far, at least) seem that pretty much any GL with the right supporting cast can beat any other on offense, you will definitely want to start working towards one of them once you have your base teams above sorted, (SEE is the least character intensive, but also one of the less flexible, SLKR is super flexible, but kind of ties with Rey for not providing many useful characters as prerequisites) so whichever flavor of GL you settle on as an end goal will probably influence the additional subsidiary teams you build as well as which GET2 Capital ship you pursue.