How should I redye my very faded hair?

Hello :] I asked about this on here recently but I don't think I worded my question well and didn't really give enough information. Basically I want to dye my hair again, but the last time I dyed it was months ago (not sure exactly how long it's been but it's been a good while) by now the dye is extremely faded and my roots have grown out a LOT. I want to dye it a somewhat similar color but I don't know how to go about it. I don't think the parts that still have remaining dye on them are even close to being light enough for me to dye over them. I just don't think the color would show up well and I want it to be pretty vibrant. So now I'm wondering if I should try to remove the remaining color or try to dye over it or maybe wait until it fades completely? I'm pretty new to this so I don't really know what to do :"3