I donno if $100k is enough for you to see "great" results, I guess depends on your perspective. $100k would get you $500k of leverage with standard 80/20 loans.
To be great with that 100k would be to, along the way of utilizing/spending, the $500k you pick up some seller financed properties allowing you to use less then the standard 80/20's (20% down payment loans), or maybe some of the properties you aquire need rehab which will give you some forced equity. By utilizing some methods which allow you to maximize your investment dollar and minimize the amount of down payments. Thereby possibly getting $800k or so of total portfolio value or possibly higher instead of what standard investment loans with 20% down payments will do for you.
larger the dollar amount of portfolio, the larger possible return obviously, assuming your ok with higher risk utilizing higher amounts of leverage which goes back to your confidence level in your experience and how good of a deal you find.