Read everything you can get your hands on. Lots of info on various web sites. Lots of on-line data from Hodgdon & Nosler that lists various loads. There are probably more combos of powders, bullets, and calibers than could be listed. Buying the annual Hodgdon soft cover magazine type manual is a good move - it describes various Hodgdon, IMR, & Winchester powders. Various manuals by Hornady, Berger, Western & Sierra are good reads and explain much. In regard to H380, the "H" stands for Hodgdon & the 380 is an arbitrary label having some reference to the powder charge for some .22 bullet loaded for the .22-.250. The on-line Western powder manual, RamShot Powders, is a good read and has good illustrations & explanations. Get a general feel of how stuff works by reading manuals and asking questions.
Be cautious, conservative & safe. Verify everything. Ask lots of questions.