Hi Back to you. Welcome to the hobby!
Another thing to consider before buying either of these things is what are you going to need to test, and how much water are you going to need to change.
When I first started up I bought Tetra pond water conditioner/dechlorinator as I knew I was going to get through a lot of water during the tank cycle, where I was replacing tank water at a vast rate of knotts. Pond dechlorinator is more concentrated than aquarium stuff and sold in larger bottles - generally you get more for your money although I had concern that I wasnt using it all fast enough as it did seem to pong after a while. I decided to move onto a dry crystal form of dechlorinator which lasts just, and as long as it is dry the formulation talkes longer to destabilise.
For test kits, have a look at single units rather than kits before buying. Some of the kits include things like C02 indication, Low pH, High pH (where you probably want just mid-range), and things like water hardness etc.
My suggestion is that you buy only the NitrIte, NitrAte, Ammonia and mid range pH, and if you need any other tests to be performed then you can take a sample of tankwater to your local store where they will happily test for a small fee. It works out far cheaper. Ofcourse if you can get a good test kit for a good price (check out any practical fishkeeping subscription offers etc) then go for it.
I dont have a favourite dechlorinator but if you are starting a new tank then go for one that has the benefit of additional water treatment such as heavy metal coagulator such as Tetra "Aquasafe". Some also have added stuff that is supposed to protect fish's skin/mucus layer but I dont know whether these work or not.
Good luck and let us all see a photo of your tank when its all up and running.
Sarah