I have been a piano teacher for many years. I would recommend finding a teacher because there is a lot to look for in your form, muscle tension, etc. that cannot be caught on your own. That said, you can usually find great piano lesson books at thrift stores for less than a dollar each. I have collected them at various different levels so I could use them when my students forget their books or things like that. Also, my kids have pretty much taught themselves out of these books. However, they have a music teacher for a mom and I can catch their mistakes and help guide them through. The Bastien method books are good, but so are Hal Leonard, Leila Fletcher, Alfred, etc. Try to stick with one series and progress from one book to the next. If you go to a music store, you can try out the music on their pianos if you ask permission. That way, you can find a good level for you. Find something that you can sight read with a little work in the beginning of the book. Then, you can work up to the songs in the end of the book.