1. Strength

1.1 Omniscience

Of course, omniscience is probably the dullest but meanwhile rather strong faction affinity in ES2, which gives you 50% of empire science bonus when researching a technology no one has done researching. One fun fact is that actually the mechanism of the bonus is rather different from that of 'Devoted' or 'Endless Researchpark and Endlessworld', which you can easily figure out from the picture below if you do a little bit math work. Omniscience also boost those science income from 'Devoted' and 'Endless Researchpark and Endlessworld', even from minor factions. So omniscience is absolutely very powerful.

To take full advantage of it, though, there is still some tips for you:

1) Bonus from omniscience drops sharply if a technology has been complete by other empire, so always try to be the first. There are some circumstances where you can' t get 50% bonus but only 25%, which is of course inevitable in the early game. At that moment, you should abandon that 25% bonus and pursue another tech to get 50% bonus, because clearly one 50% bonus and one 10% bonus is better than two 25% bonus;

2) When choosing which tech to research, always bear in mind: 'do I need this so urgent that I must research it right now' or 'by how many turn I ganna be really need this tech'. If that tech is not so urgent or by culculating you figure out after 5 turns you ganna need this but it only takes 4 turns to complete, then you can leave that tech behind and research another tech, which ai have a greater tendency to research;

3) Notice that some unique technologies always give 50% bonus (unique technologies can only be researched by sophon) and ship techs never give bonus.

1.2 Population 

Sophons can get 8 science on cold plant when boosted (with SuperSquared that will be plus 16), which is very powerful, so always remember to boost sophons and try to put them on cold plant. At 20 they give 15% science bonus, and at 50, they give -20% science cost which grants them with extremely big advantage when skipping the layers. So try to reach 50 sophons as soon as possible, using the spaceport can prevent minor factions from growing.