I try really, really hard to spend nothing. In the last fifteen years, I've probably spent under $200, and that's a highball estimate.
I will go on Reddit or Facebook genealogy groups to ask for lookups if I know a record is behind a paywall. Obituaries in newspapers, for instance, is one I will ask for.
I will go to the library in my town, and the next town over, as well as utilize the local genealogy library to help with research. This lets me access Newspapers, Fold3 and Ancestry.com for free.
I keep extensive bookmarks and notes on free resources on the internet that I consult, even if only one time. I just recently found a great newspaper archive directly from Google News I hadn't known about before. It's not the best, but it has quite a bit, and got me some information I hadn't been able to find before.
FamilySearch has most records that Ancestry charges for.
Reclaim the Records has been doing a wonderful job of working to make these public records truly public for us.
Many libraries around the United States offer guest passes, interlibrary loans, and the like to help you access their collection even from across the country.
I use GRAMPS as my personal family tree software; it is far more powerful than any other personal program I have used (and I don't want all those imports other programs have to jack up my solid, known research).
I was recently gifted a DNA kit from a relative, but I do intend on purchasing kits for a couple family members.
My costs have mostly been on books I wanted printed copies of for my personal library, ordering documents, and travel costs to get somewhere.