I'm not exactly sure how the two points above are vague and/or semi-contradictory.
Look at the range of suggested loadings for lead and jacketed bullets for your particular caliber and weight.
Whatever that range is, start on the low middle part of the range. Build a few, come up a tenth of a grain or two, build a few, come up again, build a few etc. Stay away from the fastest/highest pressure loads. That will keep you pretty much within both suggestions above. The loadings for lead vs jacketed always overlap. And unless you're trickling for precision rifle cartridges, most scales are going to be accurate to about half of a tenth of a grain. Then a powder drop gizmo will introduce a little bit more error factor. That means your finished cartridge will have "about" x.3 grains, give or take maybe a tenth to maybe x.2 or x.4 gr.
Load 'em up. Test 'em. Narrow down your loadings to what YOU and YOUR GUN agree is the most accurate or whatever shooting factor you're loading for (recoil, noise, economy, bullet speed etc).
If you want to see some WIDE variance in load data, pick a caliber and bullet weight and search on loadings for some old standby powder like Unique. I've got listings on that powder for 158 gr .38 special that range anywhere from 3.0 gr to 5.2 gr. Yesterday I shot several hundred rounds of that same bullet and caliber with Bullseye loaded from 3.0 to 4.2 gr.
Staying SAFE is the only real concern. Too light might result in poor accuracy at distance, or worst case a squib. But unless you double fire a squib, there's no danger in either of those. Too high, of course, runs the risk of high pressure problems but even that might be a long term vs immediate problem.
Sgt Lumpy