Purchase next capital ship level?

I purchase the upgrades, and most of the time it is during mid to late game, as you begin to fight other factions, then weak enemys that protect the other planets.

I find that purchasing cap ship levels can work early game for a TEC carrier blockade rush. Acquires extra strike squad and another level of blockade. Horribly expensive, but hopefully you can sack your enemy for a comparable amount of funds.

just kill some of those militias guarding planets and the cost of the upgrade will go down. it depends how much xp your ship has. if it has none its full price but if it has like half the xp to next level the price is decreased by half.

I sometimes purchase the levels if I think it's going to be critical to my survival. Usually further into the game I'll have researched Mass Transcendence though, so they auto-level to 4 pretty quickly.

Killing 2 ships at an asteroid with a cap basically halves the first upgrade cost never a bad plan to take an asteroid with your starting cap and immediatly uprade it to level 2 while its en route to its next planet.

Purchasing upgrades later in the game when your credit income is 30+ can be helpful if you want a pair of cap ships in a fleet. Multiple cap ships in the same gravity well share experience, making all of them level slower as you add additional capital ships.

In most cases though, you'll want to have one main capital ship at as high a level as possible. A level 10 capital ship with military research done is usually 3 times stronger in all stats(health, damage, regeneration, etc.) than a level 1 ship with no research at all. This can make them nigh-invincible outside of massed focus fire.

When I play, I use Marzas instead of Siege frigates, in order to make it effective I'll purchase it to level 3, and put the two points into raze planet.

First Capital ship i'll level up through pirates.