I agree. Find a good teacher, preferably one who does the lot - classical, jazz, improvisation, composition. They are rare but they do exist. A good teacher, an experienced musician, will save you an awful lot of hard work by spotting strong and weak points you won't at present be aware of.
I play a lot of New Age or New Age-esque with Gospel theme, as well as original New Age ( meaning original writings) and some popular arrangement pieces, as well as movie and stage show theme song arrangements. All of that I have taken on myself, I've had no teacher for that. However, I have ten years of classical training by a competent teacher long ago now, you would be surprised how much classical relates to other kinds of music. If you really want to learn classical you should have a teacher. If you can stand a couple of years worth of classical training you might find you like it and continue but if not it certainly will not have hurt you. That's the first order of business you need to pursue if to go down the classical road, IMO.
There is a lot of self-studying material to find. You should also listen A LOT to classical music, as you will learn so much from it. There is so much material, I cannot imagine that you cannot find anything you like! And classical music is the foundation for everything. I don't like playing so called popular music as the piano arrangements often are very dull, especially for the left hand. Compare this with Beethoven and Chopin, who wrote music suited for the PIANO. You will be delighted by what they offer, when you start investigating their works.
im trying to learn to play by ear
do you have any recommendations for classical pieces i am at the intermediate level and i want a piece that would challenge me a little bit technically.
'look at the Bach 2 part inventions. Those are not too hard at can be quite fun. Number 4, 8, 13, 14, and 15 are very nice IMO