Hey Ickyvic, I would suggest googling men's capsule wardrobe. That will hopefully give you a basic idea as to where to begin. It is really only selected shirts, t-shirts and jeans...
Once you got that covered, I would highly recommend FashionBeans, a men's style blog, and especially their basics series; they cover everything from colours, styles, fits, different types of shirts or shoes, and give suggestions for style for various body types as well. And if you can, get yourself a pair of amazing shoes, they really make a man stand out.
As a side note, I myself am of slim build and wearing shirts is kinda difficult, even the slim ones. however, wearing tailor-made vests really made a difference in making my chest broader than it actually is. Couple that with a nicely fitting blazer and you're set
