Have you read through the main site?
www.redearslider.com If you haven't, that's where you should begin.
Filters: Depends on the size of your tank - get the largest tank you can afford from the start... it'll save you money in the long run. The filter's gph should be 5x the size of your tank. so, 100 gallon tank, filter should handle 500gph. Canister filters are my favorite... at least for my turtle tank.
Conditioning and/or other liquids, depends on your water. I use dechlorinator b/c my water literally comes out white and it irritates Tomi's eyes.
Basking lights: You need a UVB bulb (very important!) and a heat bulb (you can use a regular light bulb for this)
Basking area: Should be easily accessible, allow him/her to get out of the water completely. Basking lights should be positioned above it. You need to make sure your RES can't escape.
What else:
You need a heater
Also 2 thermometers, one for the water, one for the basking area.
A bucket/hose/syphon or whatever you plan on using to fill and empty the tank.
A good aquarium stand (your tank will be heavy!)
Decorations if wanted (plants, sand, river rocks, bubbler... anything else you'd like).
And reserve money... for unexpected expenses (vet, upgrades etc).
Make sure you have everything set up before bringing your RES home.
Good luck!
