Surface plants, floating plants and stem plants are the best to soak up ammonia and nitrate. The key is finding some that will grow in your lighting, because dying plants will further pollute the water.
Water Sprite (Ceratopteris cornuta) low-med
Guppy Grass or Najas Grass (Najas guadalupensis) low-med
Hornwort (Ceratophyllum demersum) low-med
Duckweed* (Lemna minor) any
Amazon Frogbit (Limnobium laevigatum) med-bright
Brazilian Pennywort (Hydrocotyle leucocephala) med-bright
Click on the shaded names to find out more.
If you have the bulbs that came with the hood, my guess is that they would be low to medium quality for growing plants. So the lower light plants would be better options. BUT
verify that with some one more educated in plant light than me!
So you have two plant buying options:
If you have the money, can upgrade your lighting if needed, and have an idea of the plants you want for your final aquascape, you can get the plants now that you want for the long term. I would include a good bit of at least one of the above plants.
Alternately, you could also choose to just buy a lot of whatever kind you find from the above list that will fit your lighting. These fast growers tend to be cheaper plants. It doesn't matter if you like the plant or not. After your tank is stable, you can slowly start replacing it with the plants you want long term and upgrading your light if need be.
I would tend toward option #2 so as not to complicate things too much, but it just depends on how deeply and how quickly you want to research this.
As far as timers- in short, they're awesome. But you don't need
one right now. Just simply turn the lights on and off on a schedule someone more experienced can prescribe. (I would guess starting at 8 to 10 hours/day, but double check that.) If you're budgeting, my opinion is that your money would be better spend in other places right now (like plants and Prime).
*Duckweed is awesome at sucking up ammonia and nitrate. HOWEVER, it is a commitment. Many say that once you put it in a tank, you'll always have it because it is so difficult to entirely remove. So just a warning!