Also new, but here is my opinion. To elaborate what @Nick C. said, I believe that financial position and risk tolerance are on top of your list of factors.
I am a fan of multiple doors and the speed of obtaining them through leverage. If I had 300K I would either spread it out as the downpayment between 2-3 houses and have a reserve for emergency repairs.
To me, the more doors, the less risk. Just make sure that it cash flows in a good market and at least sustains the mortgage in a bad market (this lowers your risk). As long as you have a reserve to mitigate your financial risk either with cash or a line of credit, you can purchase as many properties as you want.
Being over-leveraged is bad. Say you use your 300K to make a downpayment on 7-8 properties and have to evict a tenant and lose 6 months of rent, can you cover that? Not if your spread out too thin. You have to know what you can handle and find balance.
I am impressed with people who have 50 or so properties free and clear, but the thing that stays in the back of my mind is what they could be doing with the equity in those properties? Purchase more, loan it out, or purchase notes.