Hi JT - :WELCOME:
These are a few recommendations or materials that I've read about on here that I would also recommend:
Carpet Adhesive: Henrys 263
https://www.wwhenry.com/content.aspx?id=415&View=Product&cID=93&pID=84
Carpet (too many people to list)... I used these guys and just bought the basic carpet (I was on a budget) it arrived in 2 days. They will send you samples if you want too (free)
https://www.boatcarpetcentral.com/ If you're fishing for cats you may want something like vinyl that cleans easier. Slimey carpet is nasty
Decking: Exterior grade plywood for floors with minimum 3 coats of spar urethane on it. The henrys 263 will stick to the Spar (it's been tested here). I used 1/2 inch ply (15/32 inch). Aluminum plate can be used for decking too. It's expensive, but you will never have to replace it.
Supports/Bracing: Aluminum angle is lighter than wood as far as supports go, but it is more expensive. Some guys use pine 2X2s and some use 2X4s. Hit them with spar urethane too. Rivets and Aluminum are easy to work with though and won't rot on you.
Sealant: 3M 5200 Coat all hardware with it that's in contact with hull. Also good for sealing rivets and seams.
Hardware: Go stainless in my opinion and coat it with 3M 5200. Use nylock nuts. Some of my original hardware was aluminum, but in my opinion is was weak - I could snap off the screws and bolts turning by hand.
Floatation Foam is required by law - some folks like to go without it. I have it.
Remember that anything you add to the boat adds weight to the boat. Decking, bracing and carpet can add up the pounds quick.
Have fun and be sure to post your progress!