[Cid]

If you are a caster, keeping gate memmed on your spell bar will probably save your life a whole lot more than a few more resists at the cost of hp.
If you are a melee, lots of MR is the priority for the reasons Kergan listed. Even then there are a lot of unresistable spells or ones with enormous negative resist checks. Druid magic dots and several chanter spells are unresistable as is the necro dot Splurt.
All other necro lifetaps and lifetap dots have a -200 MR check before landing and their fire dots have a -100 FR check.

Fire would still be the second priority until the mid-50s when several classes get powerful Cold spells. How much gear and hp you want to lose for FR and CR is up to you, but I wouldn't go nuts. Resists MAY help you out whereas the hp will always help out.
A Froglok Crown would help a lot, and if you're an iksar and can use Stone of Morid you can get 50 FR and 50 CR from two items; 20 from Crown and 30 from Stone.
Wiki has a resist gear link on it for finding them. I don't think it's close to fully comprehensive but it has a lot of them.