My first rifle was an SKS.
Would I do it again? No, I don't think so. I would have gotten a .22 rifle to hone and develop my shooting skills some more before going the centerfire route. I do not regret getting an SKS at all, and it's one of my favourite rifles ever made and I now own three, but if I had to do it again I would have bought my Stevens Model 300 .22LR before my first Type 56 SKS. But that's just me.
If you want my advice, I'd say get the Ruger first along with a few mags with as much .22LR as you can afford to buy and shoot the heck out of it. Once you're more comfortable, the SKS is a fantastic choice for your first centerfire. It may shoot a 7.62 round, but it's a shorter 7.62 round and the rifle is overdesigned and heavy for the round it shoots, making recoil very mild. Getting an SKS earlier and shooting corrosive ammo will also help build gun cleaning skills that will be above and beyond for other rifles where there isn't a corrosive option. If you can get a rifle clean after shooting 700 rounds of filthy, commie corrosive surplus through it in one sitting, you can get any rifle clean.
Whatever you choose, remember to have fun! That's why we're all here.