You have a lot of options. A lot of it starts with the singles make-up of your own church. If you don't have a lot of singles in your own church, you will want to try to create a program that can be promoted outside of the church to draw people in. You can also partner with other churches who by themselves may not have large singles populations, but together you could form a meaningful group.
When I worked in singles ministry, we mixed the types of activities we did, because singles don't want to just attend a bible study. Singles also are not going to be your every Wednesday night type group. We generally offered 3 six-week bible studies throughout the year, plus we scheduled a fun activity/outing every month along with 2 community service projects each year. As we grew in size we were able to offer more catered topics and activities to our singles; like our single parents, divorce recovery groups, etc.
There are a lot of creative, free ways to promote such a group.