I came across the same problem once got back in the game.
Was lucky enough to have 1 girru from back in the days that i used, but I needed to 2 more ambu weapons.
Voidwatch spamming is something you can do also with basic equip, very unlikely you'll see the pulse weapon but Heavy metal plate drop is a bouns
Escha NM, drop rate is not as bad, but still rare
Potpourri is a long grinding, I try to have Emporox's Gift active as much as I can, but still sitting at 21k after like 6 months
deed of heroism might be a good choice you can get a first voucher at 170 deeds (40 per month) quite easy to get some even with mules if you got 'em
Gobbie mistery box, only matter of luck but worth to try
Defenetly i wouldnt reccomend to buy pulse cell unless you:
- are sure to have 5 of the same type in ah
- are sure to be able to buy all 5 with the gill you have
- don't have anything better to put those gill in