Cores aren't really a necessity since I can nearly autorank once all my relays are off and the cores I have now are installed. As to the decks.... 1 month ago I had ~400, they're coming...

Finish off your Defence until you reach Energy Nullifiers Mark IIIs and get atleast Heavy Antiproton.
EDIT: You don't have to have x6-x8 Weapons to dominate PvP, x4 is good enough. Try balancing your Ship, I'm sure it'll work since it worked for me.

Ship is quite balanced as is, lots of energy, good attack, decent scan. Not as much into PvP anymore, mostly bases and NPC's nowadays

Happens when you get in your RP/h while on the Research tab, and use them on a research project before refreshing the tab.

I recommend only installing energy while in between modules. Ex: My next module will be a weapon at 40-some-odd decks, so 40 spaces worth of cores will eventually be installed until I have the required decks to put the weapon on. At the time where I have enough rank points and ship bots that, when combined with the 40 decks the energy is using, I will uninstall the energy cores for the new weapon. After that I guess I'll be repeating it for defense; at that point I usually end up with substantial energy mods installed before I have enough decks to swap them out for a defense.

If your PvPing (which you said you aren't, but answering the other guy's post) it's best to have more cannons during the run, then switch them out. During NPC it's the same thing, gun up, kill, balance out. Just helps energy efficiency...