When I was learning to turn and was in need of practice wood, I did a lot of dumpster diving and alley prospecting. Pieces of table legs are usually big enough in diameter to re-turn into spindle stock, chair seats are often thick enough to learn shallow bowl and platter techniques on, old solid wood shelving and bed headboards are perfect for plates, and look for big beams at demolition sites. And yes, I ripped a lot of old
2x4s in half and made it a rule to turn a 12" length every single day to practice my skew and gouge techniques. After the first series of cuts, I'd smooth it out and do it again. When you master clean cuts on that stuff, you are well on your way. About once a month I'd date and save one, unsanded, so I would have a record of my progress.
Get some expert instruction if you can. EXPERT, not just somebody who knows more than you. It can take literally years off your learning curve. Musicians take lessons, athletes have coaches, turners should be wise enough to not forego the advantage of instruction.
best of luck,
-mike paulson, fort collins, co