Normally I prefer to have the skin tightening done first, then follow it with dermal fillers two weeks afterwards. First, the skin tightening procedure may lessen the amount of filler that you need by decreasing the size of the folds.
Second, there is no clearcut time defined in the medical literature that should be allowed between fillers and skin tightening.
For the most part, the articles say that skin tightening does not have any effect on the dermal fillers, however, one article does report that, although there were no gross changes in the fillers after skin tightening, there was some increase in the microscopic inflammation around the dermal filler substance. All the articles state, however, that additional studies are needed to determine the effects of skin tightening modalities on previously injected dermal fillers.
Since you already have had the Restylane injection, I would recommend waiting at least six weeks before Skin Tyte. As per our European colleagues, they see resorption of the hyaluronic acid fillers after near infrared skin tightening such as SkinTyte. As for the time between Restylane injections, it depends on how quickly your body resorbs it. Most of the time, Restylane lasts between 6 months and a year. I recommend doing additional injections before the previous filler is completely gone. You will need less filler in that case, plus you get to maintain the look you like.