I would like to build a small cluster or a fast computer for hobby/educational purposes and to speedup my data processing/machine learning pipelines (so not 50 raspberypies). Things I am using now are cpu bound, I never used anything that can utilize CUDA, but it sounds like fun and I am not against it. I currently own one i5 old laptop with a broken screen, I was thinking about buying few more of similar laptops to make a small cluster or to use same money and actually build a workstation. I have peripherals but no other computer parts. I would like to spent around 1000 eur but have a possibility to spent more if I would want to/need to.
I think that for a cluster of laptops I can find good deal on some used ones, especially if they have some broken parts that are however not essential for computing (screen, wifi, touchpad etc). It also has a benefit of managing my own cluster and some cool factor. However laptops might have problems with memory and one machine might be more efficient with allocating resources and maybe even used for gaming (however I don't play that much so it's not a factor) or CUDA
What can give me more power for a buck? Any other suggestions/things to consider? Also, I don't want to require a power plant to use it