Not many guests

Catering - absolutely shell out for it. You do not want to be cooking on your wedding day, worrying about food temperatures, getting food in your dress, who is cleaning up etc etc. With a group that size, you may be able to find a private room at a restaurant who can accommodate you - often cheaper but just as nice. You won’t have to worry about cutlery and crockery, linens, furniture etc etc - all that comes with the venue.

Everything else - DIY to your heart’s content. In all honesty the best way of cutting costs is to have a smaller guest list, so you’re doing well with that already. We didn’t bother with a lot of the peripheral stuff - I got nice silk flowers for bouquets, you can skip favours, you don’t need fancy transport, you don’t need to serve top shelf liquor (beer and wine is absolutely fine).

For our minimony we had 35 guests and it was mostly DIY. My mom and stepmom helped decorate the venue, my family cooked dinner for everyone and my dad and a friend provided the alcohol. It was easy and stress free. Now for our upcoming bigger reception we are hired vendors for everything because it will be more people. If you have the help, I would save the money and DIY

We had 47 guests at our wedding and I don't regret hosting it properly with the help of professional vendors. You don't need pros for ever single detail - but having someone else prepare food and do some of the other "big lifts" will make it much easier for you to actually enjoy your day. Definitely get catered food, hire a pro photographer, and make sure your space can adequately host that number of people without feeling too cramped or too cavernous.

For a smaller group I think DIYing music is totally appropriate, and you might not need a microphone or professional sound at all for a such small ceremony. You kind find a florist that can do a bouquet for you and maybe supply you with some bulk flowers for not a lot of money. If your group tends to be pretty responsible (and it is legal to do so wherever you live) self-serve beer and wine will save you a bartending fee, and you can probably buy a few cases of each and get the job done easily without needing someone to pour and garnish cocktails. I did my own hair and makeup for our wedding (a friend helped with hair) and don't at all regret saving money on those things.