Inserts depend on how heavy a wetter J is. I would suggest you need 6 bamboo (2nd link) nappies and 2 wraps to make a night time kit, plus 6 fleece liners. If they're not lasting the night, then worry about boosters. The more expensive (and pretty!) wraps from my first link sell better on the preloved fb groups, so you can recoup some money if it doesn't work or you want to try different brands - like shoes, different types suit different shaped people. The absorbent bit doesn't need to fit too closely, it just needs to absorb, so it's the waterproof bit you need to get right :)
The fleece liner goes next to the baby's skin so they feel dry and because poo comes off the smooth fleece easier than rough bamboo towelling. Then the bamboo nappy. Then the wrap, then vest/sleepsuit/sleeping bag as normal. Wash the inner bits at 60* with barely 1tbsp powder, then at least 1 extra rinse. Detergent builds up on fibres and decreases absorbency. Don't use softener. Unless they have actual poo on, the wraps can be wiped down and reused (you only need 2 in case of midnight diarrhoea!)
R prefers the breathability of wool, so wears wool trousers (longies) with a long sleeved tee shirt, sleeping bag over the top. But he's always been fussy about nappies!