For the most part, I agree with @Thomas S. If the property is not cash-flowing at 25% down, you may have an issue. However, your situation will dictate what works best for you. For example, if this property has high taxes, an HOA fee, or you had to pay significant points/origination fees for the property, it MAY make sense to put more cash into this property before you buy another (esp. if your goal is only to buy a handful of properties). You have to run the numbers to see (see below).
Many people look at the percntage return (ROI, etc). However, you can't spend or invest percentages (a relative figure of merit). You can spend and invest actual dollars (an absolute figure of merit). So if you have another $$25K (or however much) to invest, you want to know if it will return more total money to you buy investing in the current property or investing in another property
Try running the numbers with 25, 50, 75, and 100% down. Then consider how much return you would get by using the same amount of money to buy another property. Wherever the numbers turn out better is your best investment.
Best to you.