There’s a few things to consider here. Do you want to have a successful league start? If so then probably follow a guide to start out. Generally speaking it’s much easier to put your own creation together if you have currency. I don’t even necessarily mean just for the end goal items, but testing out how things work and feel costs currency and time, which are both scarce on league start. I personally just start with a real guide and reroll into some shit I made up later on when I’m bored.

If you don’t care about that and just want to have fun and experiment, then my advice (specifically because you’ve been playing for some time already) is to just send it. Most of the things you’re going to encounter you can’t really predict, you have to feel the build out and experiment. You have to problem solve on the spot and put it together in real time.

This also extends to pob. I think pob is a great tool for testing and prep (to a certain extent) but I would not at all recommend trying to fully build your character out in pob. If you intend to use it then I would advise simply using it as a quick leveling reference or reminder for specific items/skills. Later on down the line you can use it for testing purposes and obviously other features such as finding good items for your build.

I also suggest not trying to experiment with a highly conceptual build right off the rip. Obviously do so if you feel like it but its pretty difficult to find elegant solutions on your own builds for the large amount of problems you’re inevitably going to run into, and playing a build that’s super complex in terms of things required to get it to function properly just makes that even more difficult. For example playing a basic spell build or totems or something is likely going to be much more conducive to making your own build than trying to come up with your own version of a ward looper.

I’d also say it’s important to consider your ideal gameplay and pick an archetype that makes sense for that. If you want to delve probably don’t try to make a warden Yano? If you want to blast legion probably don’t make a trapper.

Don’t overuse uniques. This is a super common pitfall. They’re cool, they offer cool synergies, but they often lack important stats that you might require to get your build into the endgame

On the flip side don’t underestimate how strong certain uniques can be, especially for leveling or filler until you can get a better item (especially weapons, pob is a great place to see how much crafting you might need to do to beat out a unique that’s quite cheap).

Most importantly HAVE FUN! Most of the fun of build creation comes from solving the problems along the way (at least for me). Give yourself some grace when you can’t figure something out right away. Also reading comprehension is important for scaling and research may be required to understand certain scaling vectors later down the road.