I have a 10 gray fisher kaitai stock. it has the acera rear derailler, what do i need to make it 9 speed? What parts? etc

Shifters, cassette, chain.

what about the derailler, does the acera work with 9?

Yes. Derailleurs know not of speeds. There are very few instances where one would need to change rear derailleurs when moving to a different "speed" cassette.

9 speed has a narrower chain, but the cassette is a direct replacement. No need for spacers or anything.

I see in another thread you are looking to replace the brakes too. For the brakes you won't need to replace the shifter/brake combo, but if you move to a 9 speed you will need to.

It sounds to be like you bought the wrong bike. In either case, the 8 to 9 speed difference isn't so great that the cost of upgrade is worthwhile. All you'll gain is one mid-step gear, not really all that important for most people. If you really need to be precise in your cadence/speed to have an enjoyable ride, I suppose so, but to just have that 9th gear really isn't a huge advantage. You don't ride faster with a 9-speed, it's just easier to get closer to "the right gear" for different conditions.

You would gain more smoothness for your dollar by getting a Deore LX derailleur than by replacing the system with a 9-speed and using the Acera.

i like the bike, i was gonna replace the ef50's anyway, so i thought why not upgrade it to a 9 while im doing it. Im a huge sram fan, im not going to go for the deore lx, i was gonna get an x7 combo on pricepoint. thanks for your help though

In that case you will need to replace the rear derailleur. SRAM X7 shifters and Shimano derailleurs don't speak the same language.

Does the rear hub need to be considered as well? Or the freehub can take on any cassettes?

You need a Shimano or a SRAM cassette.

as i sed before, im getting a combo on pricepoint