Hello and Welcome to a wonderful hobby! Sounds like you are off to a good start. I would agree with fishrfriends that the API master test kit will be incredibly valuable to you and your fish. As for a bubbler, as far as brand I think they are pretty much equal.
The next thing I would recommend is reading up on cycling (very important) and research what fish you want in your tank. Some things to think about with this are:
1.What is their activity level
2.How big will they get eventually
3.Are they peaceful or aggressive
4.What are their temperature/pH/water recommendations
5.Do they need to be kept in a school?
6. What part of the tank do they swim in
7. Do they need special decor (ex:plecos need wood, betta males need nothing they can catch their fins on)
8.What are their dietary needs
A really helpful tool for this is aqadvisor.com
It takes into account your tank size, filtration type, fish needs, etc. It's free and simple to use and highly recommended by many people in this forum community.
When getting food I recommend you read the ingredient labels and make sure whole fish is listed first and any fillers (wheat, potato protein, etc) are listed farther down the list. Quality food will keep your fish healthy and less susceptible to disease.
The last little bit of advice I would give is to make sure you set your tank up in a place that you can sit back and enjoy it. It's so nice to sink into a comfy chair with a hot cup of tea (cold beer) and relax while watching your fish.