In most govt. agriculture college, admission in BSc ag. would be based on the marks og 12 standard. The qualifying marks for general cat. would be 90%, for SC cat. marks would be 85% around. And answering your question that you should focus on getting marks ot say qualifying marks because on the basis of the marks your rank will be decided. So the qualifying marks in EAMCET are mentioned below category wise.

OC cat.-110+ marks, BC cat.- 95+ to 105+, SC cat.-95+ and ST cat.-93+. If you prepare for these much of marks you will be definitely able to get the rank around 4500 and below that for getting admission in BSc ag. good luck.