If I Don't have my shot record can I just get an MMR vaccine rather than paying for a titre test?

If you can't remember when you last had one and have no record, it is time to get the vaccine. Go to a clinic and get it done all at once. Occasionally you can get the Tdap at some place like Walgreens. But, just go to a community health clinic and get it done properly. The school may have some suggestions. Don't try to take shortcuts here. Any of those diseases the vaccines protect against could cost a lot more than just an office visit to a doctor. Consider this your first step in learning some valuable medical information.

You should not care if the vaccine is cheap or expensive. You should care if the vaccine is going to kill or debilitate you. Find out if the vaccine is needed. I think your choice is clear.