Don't be afraid of the larger tank it is less work than small but cost a little more upfront.
There are many places online that can tell you how many watts you need in a heater. Divide it into two and by two smaller heaters. It can save your tank.
The finnex led lights are a great so are the fluval led strips.
Check out the Marineland C-530, and in the carbon section use chem pure. it is a resin/carbon mix that cleans a fresh water like a skimmer cleans a salt tank. That setup will clean your tank better than most systems for twice the money.
Check out AquariumPlants.com | Live Plants for Aquariums & Fish Tanks
.... GROW-PRO: FRESHWATER PLANTED AQUARIUM SUBSTRATE
It is the best I have ever seen and very cost effective. They are also a great place to buy plants.
After you have made sure it doesn't leak set it up.
Add the soil and have at least 35 ( or as many as you can afford) plants, ready to plant. Go with Anubias and CRYPTOCORYNE First, both are easy to start in a low tech tank. The plants should be planted before you add water.
Add a dozen cheap danios and let the tank cycle. feed the fish lightly. In about 3 weeks add 2 mollies (they are hardy and will eat algae).
Pull a stalk of the Crypts lose and replant it in a new place in the rear. Crowd them and they will grow tall.
As the tank matures do 1 - 10% water changes 1 time a week for first 2 months then 1 time a month for the first year and use that time (after the change) to add a few fresh small fish. After that if you have not overloaded the livestock but have overloaded the plants you can get away with almost never changing water.
UNDER FEED, UNDER STOCK, OVERLOAD PLANTS
Below I am posting a 40 gal cube that was built just as I described
Contact me if I can help you