What time of day should I measure ketones?

Hi, just got myself a Carsens-dual meter.

The ketone strips are £10 for ten.

I don't intend checking every day otherwise it would cost a fortune. But intend to check every 5 days at first until I'm constantly in ketosis, then maybe once every fortnight.

But what is the best time to check ketones? When I get up, before I go to bed etc?

I'm only eating lunch and dinner, no breakfast.

Thanks