Nearly every strength and conditioning coach in the country relies on percentages to enforce desired intensities to athletes for certain lifts. Basically, the client would perform their lift at a percentage of their 1 repetition max. If they had a max bench press of 100lbs, and you wanted to do 3 sets of 12 reps at 60%, they would do 3x12 at 60lbs. This is absolutely necessary in most strength and conditioning environments for multiple reasons, including consistent program design as well as enforcement of intensity (speaking from experience, some people WILL slack if given the chance). So the question becomes, are percentages right for you?
The regular payments you have so far found will form the core of your household budget. You can now turn those into a formal list, either on paper or on a spreadsheet, and put the amounts into the next column, with a heading notifying the month. Before moving on to the next phase, add a further 11 columns on the paper or spreadsheet, with the headings changed to appropriate months until you have a column for each calendar month for a year. I have prepared an example budget spreadsheet to help you.