Most DIYers over-weld their projects, and all that additional heat tends to warp the job - sometimes catastrophically. It's better if a balance is drawn so that adequate strength is achieved without excess distortion.

In this video, I give you some rules of thumb and perspective into how strong your welds are likely to be, so you can draw that balance better.

WARNING: If you want to build jack stands, gantries, cranes, platforms - or anything else where 'failure' = 'death/injury': go to university, become an engineer, and get trained as a welder. If you don't want to do that, just build fun, practical stuff, such as work benches and rocket stoves (the world's still your oyster, and you probably won't die).