Vodun is not and never has been a rich person’s faith. It is about the effort, sincerity, and alignment with the Forces of Nature, not how expensive a gift is. Remember the story of Yemaya’s three crowns.
For your normal observances, if you do what you can afford, the Spirits will accept this. Just don’t be cheap with them if you really can afford to do more.
What priests charge for their services is due to the expense, time, and risks involved with doing things at an optimal level with maximum efficiency. If you can’t afford this, then there are often other ways to get the job done. They will just be less efficient and require more effort, time, and risk on your part than they would if you put the issue into the hands of a priest.
Some things simply cannot be done by someone who has not spent a sufficient amount of time studying and preparing themselves for the kind of work that needs to be done. Things that would require the use of psychoactive plants to get into a particular trance state, for instance, should only be done by experts. Same with other things that can lead to injury of the body or psyche. A layperson attempting some things can die or permanently injure themselves.
Other things though, can be done relatively safely with the proper preparation and instruction. The question of course is whether or not you are ready to do what it takes.
There was a young man who was wrongly convicted of a crime, whose sister studied law in order to save her brother. If you have the level of dedication to go through all it takes to prepare yourself to do a working, then you can do it.