dulce de leche- make or buy?

I would make it for sure if you have the time; sweetened condensed milk is CHEAP and dulce de leche is expensive. For such a low-intensity process of making it at home, I think you can't go wrong just DIYing it. Plus you'll probably impress whoever is going to be eating your dulce de leche!

Are you incorporating the dulce into the ice cream or using it as a topping?

If using as a topping, you could possibly sub a caramel sauce. Lots of great ready-made ones or make your own. It won't take 3 days - just an hour or so - but you do ideally need to use a very heavy pot, like an enameled dutch oven. So if you don't have one of those already, see if you can borrow one. Or just buy a great caramel sauce!

Or, you can buy really great ready-made caramel sauces.

Making it is fun and super easy if you have the time (just never leave it alone -- it can get dangerous if the water boils off). But if you don't have the time, just buy it. Your ice cream will still be good.