Hello :)
You're defo going about this the right way, making sure you get the right kit and doing your research- going into a shop and just buying what they tell you is normally a recipe for disaster.
Coldwater or tropical? Tropical fish are not necessarily harder to keep, but there is a lot more choice so it can be harder to get the right fish. Getting the wrong ones can cause all kinds of problems but if you get the right ones then there's no reason why you can't start off with tropical fish.
Tank size. Beginners are often sold piddly little tanks but they are really hard to maintain. Something around 60-80 litres should suit your requirements, you could have a shoal of small tropical fish. If you want more than one species then around 90-120 litres would be better. They won't take ages to clean out but the water parameters should be nice and stable even if you cock up a bit sometimes.
Feeding. Most fish will take flakes/pellets as their staple food but all fish should have a varied diet. Some like live or frozen food (you should be able to get this at an aquatic store), some will happily chomp on veg. Depends on the species.
Types of fish. Largely depends on tank size and water parameters. If you're planning on using tap water then test the pH and hardness. If it's around neutral then that gives you lots of choice. Very hard, alkaline water or very soft, acidic water will give you less choice but you should still be able to find something suitable.
Maintenance. Weekly (or more) water changes and tests are the bare minimum. If you want real plants then trimming off dead leaves etc every few days and just having a general tidy is all you need to do.
Kit. Aside from the tank you'll need a filter and heater; water testing kit (liquid ones work out much cheaper in the long run) that will test ammonia, nitrIte, nitrAte, pH and hardness; dechlorinator; substrate for the tank (playsand is v cheap) and other decor items; lighting and plant fertiliser if you want real plants; syphon tube, gravel vac (you can make one out of a plastic bottle) and bucket for water changes.
An air pump and air stone isn't essential but looks nice and some fish seem to like it.
Don't bother with any chemicals that claim to instantly cycle a tank, or anything called 'general tonic' or similar.
Hope that helps a bit! :)