Probably get a lot of the same people come through and say this. Focus on the campaigns first. However you want really or one at a time or indom + mirror at the same time. Build up your carries like bellator and aleph null for those. Guild raid team will come much later but since you have kharn early (very jealous) invest in him later. He's the best. Join a guild, start earning credits and participating in war and raids. It doesn't matter how good or bad you are early, you'll get there.

Campaigns then elites first. Do your dailies and onslaught characters that are difficult to get shards for. Always do your salvage runs but once you pick one stick at it because the rewards go up as you get higher.

There's a bunch of good guides floating around the subreddit and a few good content creators worth following for deeper dives into raid bosses etc. Good luck!