Biggest way to increase your ego is by increasing endurance, which you can do at the market.
Equipment can directly increase ur enurance if it goes in the top right slot.
Otherwise, just pick gear that maximises what you are an specialist in. By doing this, you can easily double ur endurance which really boosts ur ego.
my stats normally are now
hc c kh = endurance = ego
206 169 442 = 4629 = 7060 (specialist in KnowHow)
If I maximise for other specialties then...
hc c kh = endurance = ego
142 364 230 = 1979 = 4410
293 278 209 = 1717 = 4148
You can increase critical damage too with equipment, and it seems to have a big effect.
Boosters are also quit effective.