I grew up in a rural area and, while most of the villages had an annual flower and produce show, I can't recall any galas or carnivals.
However, when my daughter was young, we lived just over the borough boundary from Dagenham and we all loved the annual Dagenham Town Show.
It was huge, attended by tens of thousands of people and there was just about everything you could want in a gala - Dog shows, flower shows, novelty animal acts, motorcycle displays, classic vehicle shows, trade stands and exhibitions, music and performing arts, junk food and street food, all the fun of the fair. It was brilliant - until the council decided in 2012 that it wasn't profitable and put an end to it.
That couple of days every year probably did more for neighbourliness and community cohesion than any other single thing.
I no longer live in that part of the country but I understand there is a campaign group at work who aim to bring back the show. Good luck to them, I say.
Where I now live, in a small town, we don't have a gala or carnival as such but there are several "Summer Sundays" each year with music on the Green, food and drink and various traders. A good place to be with a sunhat and a deckchair on a fine (but not too hot) afternon.