1. gauge of wires i can use.
20 gauge enamel works well. Its easy to work with...
2. turns ratio.
A 3:1 turns ratio is a 9:1 impedance change. If you use trifilar winding techniques, about 10-12 turns work well for a broadband balun. Twisting 3 wires together (about 3 turns per inch) using a hand drill works well. Make 2 of the wires into the secondary and the third is the primary. Observe proper phasing!! Do a search on Google.com for 9:1 balun and get info in trifilar wound transformers.
3. are the turns spaced or wound side by side.
Spread them out evenly over the entire core best you can.
4. what type & size ferrite core should i use.
That depends on the freq range and power level. T-130 (red) works well for several hundred watts on the HF bands. Use a yellow core if you want to shift the freqs to the high side of HF and low end of VHF. Use T-50 for higher power.
5. after completion, what should the approximate
inductance be on the input & output.
That depends on the core, number of turns... Not important to know as long as you use the right material for the freqs you want to cover. You will need an ohm meter to detect the right wire to work on and make sure you get the phasing right! Go here to see a picture of a 4:1 bifilar wound balun. http://home.teleport.com/~nb6z/balun.jpg