How do I bring up dressing up without it being awkward?

Outside the moment, in daylight, as a plan rather than a surprise. Say you would like an evening that is different from the usual one and suggest what you fancy. Agreeing in advance is what removes the awkwardness — a surprise puts the other person on the spot.

What should I actually buy first?

Something that fits, in a style you would genuinely wear. Fit does more than elaborateness: the right size in something plain beats the wrong size in something complicated, and you can spend a whole evening in it.

Does it have to involve role play?

No. For most couples this is just an evening where both people got dressed on purpose in their own house. No character, no script, no costume required.

The answer

Dressing up for each other at home — where do you even start?

Start smaller than you think and start with a decision. The reason dressing up at home works is not the outfit, it is that somebody chose an evening and marked it — the same mechanism as a restaurant booking. Pick the night first, agree it out loud, and let getting ready be the event rather than the preamble to one.

What answers it

NatoriFeathers contour plunge braThe one you would not put on for an ordinary Tuesday, which is what makes the evening not an ordinary Tuesday. Wear it under something — the point is that you know.Buy on Amazon
Calvin KleinModern Cotton unlined braletteThe opposite register, and the one most people underrate. Cotton, unlined, nothing performing. Comfortable enough to actually spend an evening in.Buy on Amazon
LancômeL'Absolu Rouge lipstickGetting ready is the part that does the work. A lipstick you normally save for going out, worn for a night you are not going anywhere.Buy on Amazon

Prices live on Amazon, where they change hourly — so we never quote one. Every product here is a brand we would name out loud.

Agree the night, not the outfit

The conversation is the awkward part and having it in advance removes every bit of the awkwardness from the evening itself. Say what you fancy doing and ask what he does. Two people who have agreed on a plan are not performing at each other, which is the failure mode that makes this feel silly.

Under, not instead

The version that survives contact with a real evening is worn under normal clothes. You know it is there for two hours before anything happens, and that anticipation is most of the effect. It also means you are dressed if the doorbell goes.

Comfortable beats impressive

Anything you are adjusting every four minutes has stopped being about the evening and started being about the garment. Fit first — the right size in something plain outperforms the wrong size in something elaborate, every time.

Nobody has to be anybody else

Dressing up does not require a character or a script. For most couples it is simply an evening where you both made an effort in your own house, and that is enough to make it different from the one before it.

Questions

How do I bring up dressing up without it being awkward?: Outside the moment, in daylight, as a plan rather than a surprise. Say you would like an evening that is different from the usual one and suggest what you fancy. Agreeing in advance is what removes the awkwardness — a surprise puts the other person on the spot.
What should I actually buy first?: Something that fits, in a style you would genuinely wear. Fit does more than elaborateness: the right size in something plain beats the wrong size in something complicated, and you can spend a whole evening in it.
Does it have to involve role play?: No. For most couples this is just an evening where both people got dressed on purpose in their own house. No character, no script, no costume required.