Just some thoughts…
Volunteer in some capacity, ideally in a way that helps youngsters enjoy the hobby.
Learn a ride well so you can lead it and make it safe for others.
Take youngsters out on a good ride that you know is low risk, but they think is amazing
Whinge if your kids don’t clean their bikes, but do it anyway for them. It’ll save you money in the long run.
Long term loan out old bikes if your in a position to.
Accept that if it moves and contacts another surface it’ll wear out. Especially in the UK in winter. Budget for this and don’t skip services.
Don’t skimp on spending on helmets
Contact points are vital, buy the best you can
Learn enough about nature to enjoy pointing things out to others when you stop.
Understand you don’t need to be the best rider to lead a really enjoyable ride. So give it a go.
Seek out people trying new things with mountain biking (YouTube route guides, accommodation, podcasts etc) and support as you can. Don’t critisise them.
Engage with and support racing at all levels.