When you are building (or re-building) credit, what your score is "now" doesn't matter. The two most important things are:
- Avoid negative marks getting added to your report. This means you must pay your bills on time. (More precisely, you should never be more than 30 days late on any bill which could trigger a negative mark. Still, it's best to always pay on time to avoid the expensive late fees and interest charges.)
- You have something(s) reporting regular on-time payments to the credit bureaus every month. For example: term loans and regular payments on open credit lines.
This means that your utilization doesn't actually matter "now". In the future when you intend to use your improved credit score for some reason, then during that month you want to make sure your utilization is low, but until then it doesn't really matter. The best advice for CC (secured or not) is to only buy what you need, and pay it off in full every month before the due date. When you plan to have someone check your score in the future, if your average utilization is high, consider not using the card much for a month before so that the utilization will be closer to 0% when your credit is checked, and your score will instantly shoot up that month.