For Daz? It's 100% Nvidia every single time. Iray only works with Nvidia cards, and the alternatives aren't exactly close. Beyond that, it's hard to give you hard answer without a budget.
The problem? Good luck finding one right now unless you want to shell out for prebuilt PC, or pony up a $1,000+ for a 30 series card. Same goes for the older generation cards, they're all being gouged by scalpers (or bought up by miners, I suppose.). Shortages and scalping aside, it really depends on how long you want to wait and how big you want your scenes to be. Of course, along with your budget.
If you don't plan on having large scenes and have the patience I don't, then see if you can grab a 1070. That being said, I'd have a hard time recommending anything less than a 2070 for anything serious with Daz. Some may disagree, but just my two pennies there. Once again, problem is they're far pricier than they should be. If you're only looking 8GB or so and have a reasonable budget, then I'd say go 2070/2070 Super, provided you can find one for a good price. Or you can just wait out the scalpers for a 3060/3070. If you're in a rush/impatient, then I'd take a look at prebuilt systems (take the GPU and sell the rest, for example. Or hell, just keep the entire thing.).
