For the Flip and the Cricket, you need more than one rigid heddle reed unless you're always going to weave at the same sett or an exact multiple of that sett. For example, your Cricket comes with an 8-dent reed, so you could thread 2 warp ends through each slot and hole for a sett of 16 ends per inch (EPI), or a warp thread in every other slot and hole for an EPI of 4.
If you want to weave with two heddles, you will need two reeds of the same dent.
For variable dent reeds, you can buy one reed frame that fits your loom. You can purchase additional reed sections, but you don't need another reed frame unless you're weaving with two heddles.