Unless you have a chance to shave with a number of different grinds & sizes you will not know the difference at this stage. 5/8 or 6/8 is fine
Just buy something "shave ready" from someone that will stand by that claim.
Generally " budget" & "trusted brand" don't go together but it's not impossible.
Check out the classifieds here . Often some great deals. Straight Razors - Straight Razor Place Classifieds