It's Genshin by default, on account of it being the only one I've played extensively (albeit only for two or three months). It was surprisingly good while it lasted. I only spent something like £10 in the end - on two months' worth of whatever the daily primogem allowance was called - so I guess it was worth it, relatively speaking.
Cute anime girls (and sometimes fellas) may be a weakness of mine, but I'm pretty careful with money. I tend to resist gacha.