Ingress: From level 4 to level 5.

This is when things started to get interesting. After level 4, the AP required for each level basically doubles. From 4 to 5, it's 70,000 to 150,000, so you're going to need to earn 80k. Let's have a look at the AP breakdown.

Deploy a resonator: 125 AP
Deploy the first resonator: Bonus 500AP
Deploy the eighth resonator: Bonus 250AP

So, fully deploying a portal gets you 1750AP.

Making a link: 313AP
Making a field: 1250AP

So, making three links and a field: 2189AP. If you had to fully deploy all three portals as well? 7439AP.

So, essentially, building 10 fields from grey portals will get you almost all the AP you need to level from 4 to 5. But, as Claptrap would say, Screw that noise. Let's blow stuff up.

Damage AP:

Now, AP for destruction isn't quite as rewarding, but combined with building, it soon adds up. So, head over to the ingress intel map (google for it if you don't have it bookmarked already). You want to look for stuff like this little portal on the right. It's a level 1 portal, that's attached to 2 fields. And (if you click the mods tab) it has no mods. This is perfect. Avoid portals with shields, force amps and turrets, at least until you're level 6 or 7. Especially with shields, you'll just waste far too many XMPs taking stuff down. Although, it can be very (*VERY*) satisfying to take down a level 8 portal, it will take about 8 trillion level 4 XMPs and LOTS of power cubes.

Destroying a resonator: 75AP
Destroying a link: 187AP
Destroying a field: 750AP.

In reality

So, this little portal is worth 2661AP. Rebuild it afterwards for another 1750. And you can see how things add up quickly. With a little planning on the map before you head out, you run from level 4 to 5 in a matter of minutes.

If you're blowing stuff up like the picture here, then be prepared to use a lot of power cubes. (I'm aware I'm level 6 and using 5 XMPs, but I didn't grab any pics at level 4...)

I also found an interesting chart over at http://ingressportal.com/research/attacking/ which shows the following data:

Enemy Portal and Related Data:

Portal Level	XM Damage to you	XM Cost To Hack
1	75	100
2	150	200
3	300	300
4	500	400
5	750	500
6	1125	600
7	1625	700
8	2500	800

- See more at: http://ingressportal.com/research/attacking/#sthash.wwtAxyqY.dpuf

As you can see, a level 8 portal is really going to mess you up - at level 4 you can only carry a max of 6000 XM, so 2500 is a considerable chunk. If there are overlapping portals, and you're being hit by a couple at a time, you'll run out constantly. Pick your targets carefully. Also, watch out for Force Amps. I'll do another post on those, but essentially, they double the damage you take. Also note that as you weaken the portal, it'll do less damage with each hit.

If you remember this chart above from the previous post, you'll see that the range for a level 4 XMP is quite short, so make sure you're standing right on top of the resonators as you detonate them. Start with the level 8 ones, and work your way around.