I learned about filters by looking on Ebay too, search by category and you’ll see a whole section dedicated to filters . . .
UV Filter is a must, and then maybe a polarising filter would be your next one. They were my first 2 filters and helped a lot with regards to taking landscape shots and converting to black and white . . .
Taken using a polariser and uv filter
Orange Effect Filter
Graduated Purple Filter (Top of filter is dark purple and it fades as it goes from top to bottom)