What he is trying to say is...
You level slower as your gap increases because you gain little Xp, and your (example) lvl 32 sos weapon doesnt help much when you are over lvl 39.
He is suggesting raising 1 of your masteries, not your skills so you level with a zero gap to your next weapon, in this case a Sos lvl 42. When you reach 42 you do the cursed hearts quest to lower your masteries back down to a 9 lvl gap. Since you didnt raise your skills just 1 mastery it is affordable, to cursed heart.
This only works if you have a good weapon waiting for you. It is always most efficient to Sp farm with a new weapon, and this method gets you to that new weapon much faster.
You cant get the curst hearts quest until lvl 20, so it is uselees for farming at lvl 16 at the den.
Since you are new and probably cant afford an sos bow, than I would recomend just leveling with a gap that gives you enough sp for your build and then when you saved up enough money to buy a good weapon do what was suggested.
Also many nukers don't farm until 42 when they have there nukes + a new weapon.
EDIT* how the hell do you have a SOM+4 bow

,errr wish I had one. Well Ill leave what I said for the poor folks.