My two cents:
Combat is where things are at. Players probably want to be at least as powerful as a level 20 officer.
I'm also one of the "each to their own playstyle" people who thinks the usual advice to max out the Combat tree is... situational. As opposed to solo-ing battles as an unstoppable single ship and piloting a succession of my own flagships against the enemy fleet, I prefer to play as a seasoned fleet commander whose strength is in the full might of the fleet and composition he brings to bear. I also find building for end-game optimization while ignoring early- and mid-game boring/frustrating during said early- and mid-game, if it's not already the play style I personally find enjoyable.
it is better to abuse more and more AI cores that can be farmed... than get the skills yourself.
I also hate grinding for things (such as Alpha Cores or specific blueprints), and don't expect them to be a mandatory part of my build.
I actually never upgrade the Combat tree beyond level 1, and usually only put 6-7 points into it in total with 1 point in about half the skills which give a meaningful bonus at level 1. If I try to max out the tree, that's 1/3-1/2 of my attribute points which could be better spent elsewhere buffing my entire fleet instead of me personally.
I usually upgrade every other tree up to level 3 and focus on skills which improve my fleet as a whole (as well as colony skills, obviously). That way the effect of those skills is multiplied by every ship in my fleet which I can bring to bear in a fight, rather than only improving my personal combat power.
Leadership I usually just go for Fleet Logistics, Officer Management, Planetary Operations, and the fleet-buff Carrier skill. Occasionally Command & Control gets a few points if I get frustrated running out of command points trying to get my fleet to act sensibly. The skill for top speed boost obviously also gets at least one point, but not usually more.
Technology gets a lot of points, since most of its skills involve buffing the fleet as a whole in combat or on the campaign map. Sensors I usually leave with a single point for the Neutrino Scanner, and the weapon range boost skill gets the same treatment as the top speed booster from the Leadership tree. Most things in this tree at least get to level 2, Loadout Design obviously getting level 3 unconditionally.
Industry depends on whether I'm doing a junker playthrough or not. If so, most if not all of these skills get level 3. If not, then only Colony Management and Industrial Planning get maxed and the skills for repairing for free after battles, less chance of D-mods on recovered ships, and better salvage results, get a few points.
TL;DR
- Drop Combat skills in favour of fleet-wide buffs in Technology/Leadership which are compounded for every ship you have in combat other than the one you're piloting
- Colony skills are a must, since you can govern up to 3 colonies yourself with just 2 skill points in Colony Management even if you skip the 3rd level of that skill
- Industry skills for free repairs and fewer D-mods on recovered ships are very useful to recover from mistakes made in combat, and for fighting multiple enemy fleets in a row (or the same one(s) over and over)
- Campaign bonuses for decreased supply and fuel usage are a must
- Loadout Design 3, obviously