Just keep on practicing, that’s all there is to it. I didn’t get to where I am now without years of practice, well I wouldn’t say years, I didn’t really get advanced in building til’ about 1-2 years ago and I would build on and off.
So, I’d just keep going and practice man. Scrapping idea’s is alright, but make sure to learn from the process. If you want to speed up the amount of things you are learning, I’d suggest checking out tutorials in Blender or RBX Studio. If you are having trouble with a certain specific thing, look around on the dev forums for it. If no results, than you can ask people how to perform such and such.
If you want to get back into scripting, I’d suggest checking out Studio+, it’s very useful.
https://www.roblox.com/library/2525227847/Studio
Studio+ goes over a lot of material about Roblox Studio and has helped me with learning how to script in Lua. Of course, it won’t be easy but that’s the whole process is to learn and go through challenging moments. Once you finally learn how to make something you’ve dreamed of making, you’ll feel so accomplished and satisfied with yourself and perhaps feel ready to try more ambiguous projects. (I’d avoid F3X at all costs, not a good idea in my opinion, just stick with regular Studio and Plugin building.)
Also, don’t forget lighting when building, it makes finished showcases/projects look so much better, especially with the new environmental diffusion lighting effects. Although, I’d suggest changing the sky-box from the default one to a more complex and HD sky-box for better reflections and results. I’m not that advanced in lighting besides just setting up blurs, sun rays and blooms, however the bit I know makes the projects look much better and it’s all simple to learn.
The main priority though of when wanting to become very complex in your builds, is to learn Blender. Blender is the gateway to making better complex builds, I’d suggest checking out some YouTuber’s over Blender like who @watermelonroach recommended, “Blender Guru”.
I’ve watched some tutorials made by him and it’s helped me come a long way. If you do eventually dabble into Blender, getting your toes wet, don’t be afraid to experiment with realistic trees or nature props. I’ve seen a lot of people just resort to low poly type builds because they aren’t confident enough to make more complex assets.
If you want even more help and tutorials over Lua and scripting in Roblox Studio, I’d suggest checking out AlvinBlox, the young man is amazing at what he does and I respect him a lot for it. I would for sure check him out some time for some things to learn.
I hope nothing but success for you Cr_xstak, keep on going! 
