A lot of that depends on the field type you are flying off of, and the type and characteristics of the plane you flying. Grass fields are a lot more forgiving on props than touching one to asphalt (time to go home and re-balance your prop). the only difference between a trike and tail dragger is that you have to measure the clearance on the tail dragger with the wings level (position that the plane will be in at take-off and landings). but usually 1"-2" is enough. On a trike plane, make sure you take into account that the nose gear can flex on touchdown. so that if you have a bit of a rough landing you have room for the gear to flex without touching.

I had a .15 size shrike that I kit bashed and put landing gear on. I only had about 1/4" clearance on the prop and never landed the thing without touching to prop and killing the engine. important lesson here?? Shrikes don't need legs!!! lol

good luck