Brant - whenever I make a kit that does not come with skins I feel duty bound to at least add 4-8 oz. of raisins or currants or a more specific fruit, depending on what my wife (the baker) has on hand, and what the wine varietal's flavor profile suggests. Winefolly is a great source for that and here is what it says about Sangiovese:
Guide to Sangiovese Wine and Pronunciation | Wine Folly so for Sangiovese, if I did not have skins on hand, I would add dried cherries, dried plums (aka prunes), strawberries, or figs based on this:
FRUIT: Tart Cherry, Red Plum, Strawberry, Fig.
If I did not have or did not want to lean into any of those flavors, I'd just add currants or raisins like you suggested, 4-8 oz. of currants or raisins, it will add a bit of sugar and a bit of 'structure' (tannins, mouthfeel, etc) in addition to a bit of a sugar/abv boost.
I did make a Tavola Sangiovese myself so I checked my notes. Turns out I bought a Forte and a Tavola at the same time and reserved 500 grams (just over a pound) of skins and seeds from the Forte kit, so I just added that to my Sangiovese. I did an EM as well, 4 weeks total from start to secondary.
If we had dried cherries on hand I likely would've added those but I think we did not so I just stuck with the pound of skins and seeds.
Assuming you have none of the cherries/prunes/strawberries/figs then I'd just go with 8 oz. of currants. Good luck!