You can go so many direction with a 55gal tank and depending on how much you want to spend can make a difference too....you can go low tech low cost (my personal favorite) or high tech high cost
With planted tanks one of the most important things to get for success is the lights-I use plain ole shop lights from home depot for $9.99 hold two bulbs and I get the GE brand daylight 40w 6500k bulb for another $9.99-this will give you a bit less than 1.5wpg but it is enough for most of the low to mod light plants
Next is the substrate...OMG this can cost you if you want or go to home depot and get a couple of bags of pea gravel or pool filter sand or play sand or you can even go natural and use dirt or potty soil but with the NPT method you have to start out with lots of plants and I mean lots of plants a few won't work...I am talking 80-90% of the tank planted
Filtration-in my opinion/experience they all pretty much the same the only difference is the type of media you can add-you want to limit water agitation at the surface like with bio-wheels so you don't gas out the CO2 that is naturally in the water-but water movement is important and it make the tank look neat too with the plants swaying in the tank....
Heater-I would get a submersible type 100w at least-I am not brand oriented to me one is as good as another.
Driftwood- I collect my own..cheaper or you can buy a nice big piece and you will need driftwood if you plan on adding a pleco for their digestion needs...bushynose is the best and won't get to big.......and rocks....again I collect everything local and use
Plants-what are your plans on them as far as where are you going to get them-if you are ordering on line get me the link and I will go through it and find/list all the plants that will be good for what you want to do
Another good place for plants is a local aquarium club-tell me your state and I can look one up for you if you don't already know or a member of
The list for plants is endless........
If you are going to a local pet shop to get them get a list from them and post it and I can help you out
Fish/livestock.....again depending on what you want-go to the fish shop or on-line and look at what you like and research...... a lot of ma and pa type shops and even some of the box pet shops will special order both fish/livestock and plants for you with their next order.....and aquarium clubs are good for livestock too especially shrimp and snail that are hard to find.....all depends on how big of a hurry you are in.......
Water changes-a good rule of thumb is 50% weekly and depending on how many and what species of plants and livestock you have that can change too...
What do you want...a planted aquarium or aquarium with plants or natural planted...maybe a mix...what is the focus-this will determine the ferts needs and water changes for that matter...