Discone antennas are generally a decent approach for reasonably wide band coverage although they aren't always the best antennas...a perfectly good place to start from though and you will probably find decent reception with one.
Getting your antenna up high and in the clear is always the best bet as it will maximise the performance of what you have. Remember that the antennna is probably the single most important component of the system overall.
Regarding a preamplifier, these can be somewhat of a double-edged sword. They can be very useful if done correctly (not too much gain, filtered appropriately to prevent interfering signals becoming an issue and fitted at the antenna) but can also make overall performance and satisfaction much, much worse. Don't worry about a preamplifier until the point where you really need it.
The second most important part of the system is the coax feeder; do the best you reasonably can here since it would be a shame to ruin the performance you could get by throwing all of the signals away in lossy or damaged coax. Here there are a lot of options but good quality coax is important, although decent cable/satellite TV coax can be very good (think CT125 or similar) since this has good performance even though there will be a small mismatch loss. Remember that although your antenna and receiver may claim they are 50 ohm impedance, in reality most wide band receivers vary a lot so using decent 75 ohm satellite TV coax works very well. Just make very very sure that the connectors are fitted properly, safety grounding is done as needed and any connections are properly waterproofed.
I hope that helps!
