What type of fabric are you using? Dying is extremely dependent upon the type of fabric you are using. Among Natural fibers, Cotton, and Linen and Hemp take up different dyes than wool and silk. Some synthetic fabric will take dye very well like Rayon, others like polyester and nylon are very difficult or impossible to dye.
Here is a basic primer on dying fabric.
[url = http://blog.wardrobesupplies.com/2014/05/21/home-fabric-dyes-101/]How do I Choose Which Fabric Dye to Use?[/url]
and a good source for fabric specific dying agents and fixatives:
[urlhttps://www.jacquardproducts.com/dyes/]Jaquard Products[/url]
RiT is a good general purpose dye and will work OK for most purposes but it is always better to choose a specific dying process for your fabric.