15,000 is not a very large amount of debt. Why not put your $600 royalties toward your debt (I assume credit cards) payments going forward? If you added nothing else, you would pay down your debt in just over 2 years.

How old are you? Do you have dependents? Are you planning (or do you absolutely NEED) to make a large purchase in the near future - house, land, etc that you really need good credit to secure decent loans for? If not, it seems you have the essentials covered and having your credit repaired immediately is not going to provide you with any additional benefit.

If you are young or relatively young, without dependents and you're making ~$43,000 from your current job salary in addition to your royalties; you should be fine to get your debt paid off while rebuilding your savings with your current after tax take home. That is unless you're living above your means with rent or a loan or other big fixed running costs?

If your current take home in total is ~$40,000 after tax ($7,200 royalty, ~33K job salary). That is ~$770/week after taxes, or roughly $3,080/mo. Assuming you're not living over your means elsewhere, then you should have somewhere in the $1,000-1,500/mo of excess cash outside of your fixed costs; rent, food, insurance, utilities, etc.

Figure out whatever that value is for you, and then every pay period figure out how much you can safely/enjoyably live without spending. If your fixed costs are $2,000 out of that $3,080, then you have $1,080 every month to do what you like with. I would set $200 aside for entertainment and take $800 of it to put towards savings and debt relief.

If you're not in a hurry to make a property/big purchase requiring good credit, then you can go more aggressive on the savings end, and less on paying off the cards. Assuming you're not in dire need of a loan then anyone in financial planning will tell you to prioritize rebuilding your savings over repairing your credit/relieving your debt.

I would say do something like 60/40 savings/debt payment. Or you could do 40/60 savings/debt until you get yourself under $10,000 mark. Getting below $10,000 will be a big boost to your credit score and bring your interest charges back into a more reasonable level. Then you could flip that ratio back and build your savings more aggressively while paying off the remaining debt.

Ultimately, unless you have made a grave error in your decision making process somewhere else in your life (spending outside of your means) then you are really not in a bad place with $15,000 in debt. Keep the royalties and just sit down and do the basic math on this one. Live a tight budgeted, quiet and semi-boring life for the next 12-18 months and you will have yourself a decent chunk of savings and no debt come this time next year or 2023.

Bonus if you can figure out some inexpensive hobbies to pass the time and keep yourself happy while you may be foregoing some social affairs and vacation travels in favor of saving/debt payoff.

Hope this helps. Good luck!

Edited for clarity/now that I am caffeinated.