Sacred gold or storm silver, which should i play first?

The adjustment coming from vanilla is that you can't just carry the whole game on one overleveled starter. The gym leaders have real movesets and held items, so spread the exp around and actually use the items you find. Save before every gym and you'll be fine.

they're basically the same hack, one built on HeartGold and one on SoulSilver, so the difference is the same as the originals: a handful of version exclusives and which legendary is on the cover. pick based on the exclusives you care about and you won't miss anything else. just know trainers have full, properly built teams, it's a lot harder than vanilla.