The quality of the skins are not a problem, imo. I like the direction they've taken by making the gemstone skins mainly Hextech skins, something I thought was going to be the theme when they initially released Hextech Annie. However, the limit of the system in this regard, unless you really like the skin, most gemstone skins may not interest you unless it's one for your main/ favorite champ.
Carlos teased a new reward system linked to skins coming later this year, around mid-season, perhaps it will also make use of some of your gemstones, idk.