Besides looking bad, dirty brass sometimes can actually scratch a sizing die, even a carbide one. The scratches will then be transferred to every case that passes thru the die thereafter. I recommend cleaning all brass between loadings. Not usually necessary to trim handgun brass or scrape primer pockets unless they get truly crusty.
Most .38s are regulated for 158 gr. bullets and I like to use 125-130gr RNL in my 9mm, because my pistol feeds them well and shoots them to POA.

YMMV
Larry