For HR budget, you have to consider first your oraganization's business plan and annual
target...Based on this u have to prepare your manpower planning for that year (monthwise) like how many people u required more, in what level, salary and other benefits, and arrive what will be the cost of each recruitment (addition / replacement), then budget for Training, then plan on Travel (domestic and international),and other administrative costs / expenses..

It is always better that HR expenses should not be more than 50% of the overall expenses...

Hope this has helped ; )

Raghu