Sherry, you can post the Gardner line that you're working on on the Gardner Surname Study, on the Gardner Y-DNA project or here on G2G. There may be others interested in the same trees.
As far a DNA tests go, the autosomal test offered by Ancestry, MyHeritage and 23andMe can be taken by men or women and are great for cousin matching and connecting trees.
The Y-DNA test offered by FamilyTreeDNA is specific for males and is associated with patrilineal surnames so is useful for surname studies. FamilyTreeDNA hosts surname studies based on Y-DNA test results. My FreeSpace Gardner Y-DNA project is essentially a summary of the FT-DNA Gardner results which doesn't have trees but only some information about earliest known ancestors.
If there are potential male Gardner testers out there, FamilyTreeDNA currently has a sale for Y-DNA and other tests through the end of the month with the basic 37-STR Y-DNA test for $79 ($40 off). This is a good start to see if you match other testers in the surname project.