First things first means to do things in the proper order; do not skip things that you should do first.
The most important task get priority.
To focus on the appropriate order in which to do things.
1. Let’s go to a jazz bar afterwards! But first things first, let’s pick a restaurant for dinner.
2. I think you planned your colour palette well, but first things first, you’ve got to pick watercolour or acrylic.
3. I can’t wait to graduate from school, but first things first, I should study for my final!
4. I need some groceries, stop by the bank, and send out emails, but first things first, how about some coffee?
first of all, firstly, foremost, immediately, in the first place, primo, up front