What I did when I was 14 was get myself a nice spec list with a calculated price, ask a local small company that services in IT to build be the PC, they charged me the correct price for the parts plus a small fee for the assembling process, and off I went.
Back then I must have saved about 600€ on a 1150€ purchase (the computer and the peripherals, plus like 20€ for XP). That small company has always helped me whenever I needed help, but I usually don't, so I cannot complain on the support from, and I'm pretty sure I'd get a much worse service on big name companies. Specially considering my personal experience.
I've been doing this ever since. I never assemble the computer myself cause I'm a bit scared of the thermal paste for the CPU, and for a 30€ fee, it's easier and I save time if I just have them do it.
So I can say that, if you can pay a small company that works in IT at the enterprise level, or just some small IT shop that simply builds custom PCs, you're much better off.
Otherwise, I don't think building a PC yourself is a good strategy for the inexperienced user. But that experience that you may be lacking is easily "borrowed" from a friend or the internet, if you ask the right questions ("will this work") in the right places (here, for example). And if you listen and don't think you know better, despite having absolutely no background knowledge on the subject. If someone tells you a GTX760 4GB is a waste of money in comparison to the 2GB version, YOU LISTEN TO THAT ADVICE AND HEED IT LIKE IT'S GOSPEL!!!
Thanks for reading.