Best Age Gaps?

My son is 3 and we've been TTC since October, and my cycle is still adjusting a from miscarriage in November.

My main question is what the best age gap is, your kids ages and how you're finding it?

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Backstory to why I'm asking if anyone's interested lol

I'd like another baby ASAP as I think 3-4 years is a good gap, but we're in a weird situation. We're saving to move UK to Australia when my partner completes his work contract in 2025. So looking to move early 2026 (depending on visa timelines etc)

I'm stuck between having a baby ASAP, and my mum looking after them part time from age 2ish while I go back to work (shes retiring soon), then free nursery full time from 3 and I can get a possible extra 1.5 years worth of savings/income for the move, or wait and work full time now and move with an extra 3ish years worth of savings/income, then have another baby but have an 8ish year gap. Savings without me working at all is doable but more savings the better.

Options are better age gap, or better money.