As much as you can for as long as you can, so long as it is a financially responsible decision.
Guys use anywhere between 3-20 IU, on average. The more you use, the better and faster your results. I couldn't say what a "good" dose is for you because I do not know anything about your personal situation.
Generally speaking, around 5 IU's will produce consistent results in fat loss and muscle fullness (growth is slow with GH compared to AAS), but you will need to run it at least 2-3 months to notice anything substantial. Results should start to become noticable in 3-4 weeks.
Around 10 IU and results come quickly. Fat loss is rapid and increases in muscle fullness is very noticable. Growth will occur faster than at 5 IU, but still significantly slower than with AAS. Visually impressive results can be seen in just 6-8 or so weeks, although using it for several months will produce much better results.
Above 10 IU is considered a very high dose. Hell, 10 IU is a high dose when used consistently. You better have some cash to use 15-20 IU of GH per day. That dosing amount is completely unecessary for basically everyone. I could understand some professional BB'r using that dose, as lipolysis will continue to increase as the dose rises, but IGF-1 readings max out at about 10 IU per day. For most people, 10 IU is the most they will ever need. Even many pros stick with around 10 IU. The recent claim that all pros are using 15-20 IU a day is complete horeshit.
Dosing GH 3X per day will produce steady blood levels of the hormone all day long, if dosed 8 hours apart. This will also result in more fat loss than with less daily injects, as higher dosed single injects can result in a massive increase in lipolysis all at once. In these cases, the body often isn't able to oxidize fat at the same rate lipolysis is occuring. This prevents the body from maximally capitolizing on GH's fat loss potential.
2-3 IU, 3X per day, works very well for most people. Even if all you have the money for is 4 IU per day, you will notice decent results over time.