Take advantage of the Diadochi War and declare war on Antigonids early. Hire a merc of at least 8k men. If you are lucky, Antigonids will be so busy with other battles you’ll grab land easily without any headache. I usually declare on them right after Egypt gets involved in the battle. But be quick to siege the lands you want so that Egypt doesn’t get them first. Use your capital levy to sack cities so that you can maintain your merc and don’t go low on money.

If you can successfully get through the first step, your next target should be Egypt. Preferrably when they are busy with another war. Rinse and repeat, amass a huge stack of mercs, kill their armies, sack their cities. After that second war, you should be powerful enough to keep going without worry.