I would suggest doing leves 43+ and also when you cant find the mats you need for the synth. It is also best if you leve with a synth that is 8-10 levels above you with impovise and the necessary brand with the most control gear possible. The reason for doing leves 43+ is that most of the time it is expensive to buy mats that high of a lvl. Another easy way to lvl off of leves is if the leve is giving you really bad exp then hasty hand it just to get the quick exp and free mats and do regular synths on the leves that give you decent exp for a full synth. Another thing to consider is to set you homepoint at the city you are basing your leves at and to lower the anima at the main high lvl aetheryte crystals that you have your turn ins at, this will maximize the amount of anima that you will use, in case you dont do hamlets and dont have infinite anima. Another thing to look for is a leve that you can turn in to an npc that is located in the city (i want a dual box mule with a 50brd for swiftsong so bad), this can make your crafting life aboslute cake. Hope this helps out, gl xD.