For you: save money and don’t worry too much about getting ahead now that you’re already done school. Relax and enjoy your time off.
For others looking at this thread who still have a year or more of school left (and are full time so extra classes don’t cost more): if you can take classes that will allow you to be exempt from them in vet school, do that. Penn, for example, lets you test out of histology and developmental biology if you’ve taken them before. Other schools probably do the same for some classes, but obviously that would depend on the school.
Even if you can’t test out, I personally felt that taking comparative anatomy, physiology, parasitology, genetics, microbiology, and a bunch of animal science classes helped immensely. Others have said taking immunology was a big help, and I’m sure they’re right.
My advice is basically this: if you can take these classes to fulfill undergrad requirements and it’s not going to kill you to do it, then definitely do it. If it’s too much trouble and detracts from your ability to do well in other classes that you need to graduate, then don’t do it. People like me who took a lot of these classes in undergrad have found it to be pretty helpful so far. Most people haven’t and do just fine.