You are fortunate not to have much work currently and have some free time to groom yourself to become a better HR professional. I congratulate you on your proactive attitude to make the best use of the time and would like to suggest the following:
Reading - Journals and books relevant to HR. Read up on topics that you feel are especially important in your current job. Read up on topics of your interest as well as on those topics in which you would seek more inputs /clarity.
Planning - Identify areas of work where you can standardize and/ or simplify and/ or strengthen the existing system. Prepare formats that are relevant to your varied activities both in physical form as well as in EXCEL sheets. You can also plan out things to strengthen the administrative matters, make the reception area more welcoming etc. Plan a welcome note for new entrants incorporating the do's and dont's that forms part of the corporate policy including the leave policy, the outstation duty policy, the different allowances etc.
Notings - Make a noting of areas of improvement / some new initiatives that you can propose. Note also the frequent complaints / laments of employees as also the suggestions that they could be making in the passing. You should also make notings of good HR practices that you red about and which can be possibly implemented at the current workplace.
Writing - This is different from notings. Here your focus is to write scholarly articles related to HR which you can send for publications. If published it would add to your CV value. You would also learn the art of researching and doing searcher related writing.
Learn from the functional specialists - The salaries and Wages department, the Learning and Development Department, the Recruitment specialists, the Administration Department personnel all of them can give you an over view of their functions.
Don't limit your thinking. Hence be open to new ideas, explore avenues beyond your immediate job profile and start implementing what you can initiate immediately.