You generally want as high of an initiative as you can reasonably afford. Shadowrun's combat is very offense heavy and a good rule of thumb is that someone can take out someone of equal optimization* on their pass. Therefore you want to go first to be the guy to go first. However, there is no set value to be the guy who go first since it depends on who you're facing.
If your GM makes his own NPCs, then I can't help you too much with the expected value. In my experience with the pre-made NPCs, the "tough" ones like Red Samurai and Tir Ghosts have between 10-13 Initiative. Generally they're lower.
As a PC, the highest value you can easily** get is likely 14. That's Reaction 5, augmented to 9 via cyberware, and Intuition 5. I recommend at least 10 since that's Reaction 5, augmented to 7, and Intuition 3 which is extremely easy to reach as a cybered character.
Theoretically with magic, you can get a much higher initiative. You can increase Intuition as well as Reflexes to your augmented max via Increase Intuition/Reaction. Secondly, Increase Reflexes boosts your Initiative directly so you can cap out your attributes and then get a bit more. The end result is a value of 21 (Reaction 9 + Intuition 9 + Increase Reflexes 3). However you'll rarely see this in play since it requires 3 decent force spells sustained. But it's possible especially at higher optimization levels. In practice, most mages have only have 0-2 spells sustained and have less points maxing out their reaction and/or Intuition. Thus they either have lower Initiative than mundane combat characters or about the same.
One thing to keep in mind as well is that you can spend Edge to go first. Thus one tactic is to be lucky and beat everyone else who didn't spend Edge. However, you will have to compete with other edge spenders so you want at least a decent Initiative.
IPs are a different matter. The value of IPs varies a lot from fight to fight, but two major variables are your side's offensive power and the relative size of the two sides in the fight. The more powerful your side's offensive power, the less valuable IPs are. This is because as offensive power increases is you'll more likely just take out the other side before later IPs come up. Instant AoEs such as airburst explosives and spells will especially cut down on the value of IPs in this manner. If you're badass enough to take out 2 enemies per IP, then IPs matter less.
Relative size matters since it puts a bound on fights where the number of IPs matter. Generally the more equal in size the fight is, the more IPs matter. For example, if you outnumber the enemy 2 to 1, you'll just wipe them out on the first pass. If you're outnumbered 1 to 2, you'll either be wiped out by mass fire or their attacks are weak enough that it doesn't matter how many shots they take.
In my experience, the IP count you need for any given fight is generally 2. However, every so often I'll see a need for a third IP. Since the cost of getting the third pass is low***, I recommend grabbing Wired Reflexes 2 for most characters. If you have a good reason like being a full replacement character or otherwise super short on cash and/or essence, you'll do fine with Wired Reflexes 1. Mages can get a force 3 sustaining focus for Force 3 Increase Reflexes for similar effect though at different drawbacks.
*- This generally becomes less true on the very low end (3-4 dice with Streetline Specials low end) and against high Edge highly armored characters.
**- Easily being a human/elf/ork, not hardcapping either attribute, and not messing around with SURGE, Exceptional Attribute, or Genetic Optimization
***- Wired Reflexes 2 costs .7 essence and 11,000Y more nuyen than Wired Reflexes 1 and Reaction Enhancers 1.
