Normally, well, most always I choose the Freighter. It comes with an omni laser cannon so that part of the hunt is already done. So, the very first thing I try to buy is the laser collimator to enhance the cannon 75%. If I find a weapon enhancer ROM I'll use it but I generally like trying to save it for the omni Turbolaser, which is the next weapon I'll try to get unless an omni particle cannon can be found. Yeah, I'm omni!

Then I go for shields. Most often, a Class II can be found in loot (usually in the first system) and I'll have it installed and sell that Class I ASAP. Then I aim for the 50MW reactor so to gear up for my pref shield, the Class III. I've taken the Class III all the way to St. K's many times before upgrading. Will also use a shield enhancer ROM as well but again, I try to save it for a better shield (usually a level 6). That's hard to do without Rowena.
Armor in the early game is used by chance from loot. I'll rarely buy any armor but instead, will install any better armor from loot-even if it's already damaged, it can be repaired cheaper than buying new. So generally I'll end up having a mix-matched set of armor installed until a decent set of a matching 4 can be found. And I won't use any armor enhancements until I find a good matching set of armor. Good places to find better armor are the arena and Charon and independant armor dealers.
The secondary weapon is usually the NAMI, but rarely will I buy one as they can often be found in tact, in loot. And missiles are bountiful in Charon, so there's plenty to go around.
Usually by the time I jump to Rigel and enter the arena for a few bouts, I'm able to afford the 100 MW reactor-which really eases the tension off from the Class III shield and Turbolaser power drain on the 50.
The Freighter being the slowest playership, it needs a boost so a thruster is always installed if one can be found. It'll get upgraded along the way.
If a patcher arm can be found I'll snag it until I find the spider (which is rare but possible pre-St K), and will usually remain installed for the rest of the game. I think it's the only pre-St. K item that'll remain installed, as everything else will get upgraded along the way.
So on average, by the time I reach St. K's my Freighter will be rigged with a Turbolaser, NAMI, Class III shield, any armor averaging 45+ HP, 100 MW reactor, thruster and patcher/spider.
How do you usually rig your ship early in the game?