I knew about BTC in 2016 and I was damn broke at the time but still I went to a computer store and purchased old GPUs like hd7870, hd6970 with few gtx770s, my mistake was I never did any research than just using a mining calculator, I don't know that 2GB will become.obsolete faster than 4gb but I still did it anyway, out of 15 coins that I mined only electroneum saved the day, I was able to get 90% of my money back before February 2018 and that's because I was one of the first miners on electroneum pool at that time, after bear market took over I sold all GPUs to small PC gamers, here are few things I've learnt
1. Crypto profitability isn't ever going to be stable.
2. As time flows by difficulty will rise which will result in less rewards.
3. Algorithms are of different types, some works with core clock and some with memory clock.
4. If you mine coins at early launch date you can make better profits depending on how good the project is.
5. As time goes by some GPUs will become outdated.
Fast forward to 2022 I am now a proud owner of a better rig built by me with the mixture of RTX3060ti, 3070s, gtx 1660s, 2060super, picture is available in my other post here, this is just the beginning as I have found a new home in crypto, mining is now my hubby and I'm looking forward to correct some mistakes I made in the past e.g mining the wrong coins.
https://bitcointalk.org/index.php?topic=5388051.msg59408117#msg59408117