You don't need to be an aquascaper. If you can keep fish you can keep plants. The problem is most LFS mostly sell difficult high light plants and submerged house plants so you come back after a month to buy more. Start with easy low light plants such as Java fern, Anubias, guppy grass, Crypts, Java moss, dwarf hygro, there are many more. Check Craigslist or the local aquarium club, many hobbyists give away cuttings.
That's just diatoms. You can easily wipe those off with your fingers. They appear in low light conditions and are a great food for lots of algae eating fish and snails. It's harmless but you don't want it to cover plants as that prevents them from growing.
No by all means don't get a pleco most of them grow as big as your tank. Clean the plant, get some snails, then improve the conditions in your tank for plants, you want to grow plants, not algae. It is just about providing the right conditions for plants. If you don't have that, algae will take over.