The consensus seems to be that hobbyist mining for short term profit is over unless you have access to very cheap electricity. Of course playing with trainsets doesn't neccessarily make financial sense either, and as a way to learn about digital currency mining is a great start.
For example https://cointerra.com/product/terraminer-iv-used-bitcoin-miners/ offers a 1.6TH/s machine for $1500 and its probably going to cost $200 per month in electricity minimum. You can model some scenarios here https://bitcoinwisdom.com/bitcoin/calculator but its difficult to see how this can make money unless BTC rises in price or difficulty turns flat or negative.
If you are bullish on BTC then maybe simply buying some and using it to make purchases is a good start.