It really depends on your credit, the specific loan type and the lender. Having "reserves" means having something left over after your down payment and paying your closing costs. Sometimes the funds you have in an IRA or 401K account may be considered toward your reserves.
Another strategy is to ask the seller to pay your closing costs in your offer, provided the home appraises and they agree.
Start by discussing this with your lender. You need to get pre-approved before you can seriously consider shopping for a home. Your lender will discuss your loan options, credit history and the requirements you need to meet in order to buy. Then, have your lender share their findings with your agent so the best strategies can be employed with any offer you write.
Best of luck.