Sir Ganksalot's Gank Evasion Academy uses an A-rated, un-engineered Cobra as the baseline. E-rated equipment is really just placeholder, honestly, and won't stand up to much of anything at all.
Of course, all of this is part of what makes knowing what you're actually facing so difficult. You can see if a ship has shields or boosters, but you can't see what rating they are. You can see if a ship has a docking computer or supercruise assist, but can't see if the ship has hull or module reinforcement packages.
Then there's the variables of the gank ship you're facing. The builds vary there quite a bit, from things like Kraits with frag cannons to "Meta FDLs" with PAs and rails. Then there are meme builds - using Pack-Hounds or even mining lasers. Some gankers use groms to disable FSD drives, others rely on maximizing their alpha strike so they can kill before the FSD cooldown ends. Some plan on doing "reverski" (flying backwards at high speed while firing from long range).
In many ways, gank builds and playstyles can be more creative and diverse than the competitive meta ships, which tend to get winnowed down to just a couple variations and a specific set of skills for facing same.
The long of the short of it is that Open is full of all of the above, and it's constantly being thrown together in wildly varying permutations. In terms of surviving a gank, A-rated shields (ideally, prismatic shields) and as many boosters as you can carry, and some hull and module reinforcement packages, is probably a decent baseline. Beyond that, engineering the shields and boosters, armor and HRPs is the next step. That, combined with good evasion skills, should see you able to survive the vast majority of gank attempts.
