It does not really matter.

Many beginners find A2OJ ladders useful just to have some "path" to stick to. The ones near the bottom only show you one task at a time, which means you have to actually solve everything in there.

One warning though. Please don't have a mindset of "if I do these X things, I will succeed" or go looking for some sort of checklist. This very easily leads to a situation where people tell themselves they practiced while actually, they haven't done anything productive.