When fighting Exarch use Flame Dash to dodge Fire Balls
When fighting Infinite Hunger - Use Soul of Arakaali / Soul of Shakari
The only required items to kill those Bosses are Shroud of Lightless / 6-link Mace with good pdps
If Overlord Cluster jewel is expensive - buy one more two-hand cluster jewel
Maven and Uber Elder cannot be killed on a budget so you would have to buy a service on TFT in order to get the voidstones
If being frozen time to time annoys you - use Soul of the Brine King / get a 40-50% chance to avoid being frozen on an
abyss jewel in your belt
Ancestral Cry is a good way to increase attack range and make hitting with static strike safer, you can fit it if you have no portal gem / have 3 socket shroud, should be put on left click, take Call to Arms