If you have Absorption Shields available, praise the RNGods and build them - you need to uncover 2 separate techs from ruins, which takes a lot of luck or a lot of installations to sift through.
Shields are an optional tech... like Cloaking, Turrets, Gauss (railgun PD requires pretty much no research), ECM and a second anti-ship beam line. Can be good if they fit your needs, and investing into one or two won't hold you back too much because of the way research costs scale. I wouldn't go for all of them, and I'd wait until I have the basics covered to the point where the next tech seems painfully expensive.
How you should split shields and armour is up to debate. Minimal shielding is fine (just to protect the paintjob from the occasional leaker, or avoid shock damage in case of single big hits), so is all shields and minimal armour on larger ships that invest a lot into protection (can take moderate damage almost indefinitely). I don't particularly like an even split, seems unfocused.
