If you are digging yourself into a hole by not following a skill tree build, so how hard will it be to fix your skill tree once you have more knowledge of the game? After you can help make your own build you farmed some PoE Currency Cheap
so it ought to be pretty easy to begin.
It depends. If you have fun and enjoy it, go for it. A lot of people say that fucking up your first character is a good thing because you learn more about the game. For example, you learn just how important defences (like resistances and life) after you've died 100 times on your way to level 70 on your first character. This way you're also able to try out different skills and see which you like and then pick a suitable build for that skill for your second character. Unless you have leet amount of PoE buy Currency
so you CAN afford niche builds
If you're okay with hitting a wall but at least seeing how far you can get then go ahead. Following a guide will help a lot in easing you into finishing the story and starting the end game. If you like min-maxing then follow a build. I still follow builds and I have a pretty big chunk of time in PoE.
You probably are digging yourself a hole for not following a skill tree. POE is mad complicated, the wording on some skill and nodes on the skill tree makes it complicated. I say follow a skill tree for your first build and than start experimenting after. Look up Path of Building also.
No one can figure out everything about PoE so easily. But if you are ok with hitting like level 50-60 and not being able to progress further, go for it! My first toon made it to 70, lots of moons ago. But It sucked so so much compared to my actual chars now or to any build guide I followed.
Fixing the skill tree is not easy for a begginger. U get somewhere around 20 refund points from the story, but then you will have to use 1 regret orb for each refund point you need, and you'll need at least more 40 or 50 and they are pretty rare and moderately expensive orbs.