@bluespottygerbil I started with 3.5kg back in January for epic 1, but did some exercises body weight only (definitely windmills!). Only got to end of week 8 but then restarted with 5.5kg for mostly everything.
I'm now trying iron and going up and down the weights like a yo-yo! Using DHs barbells for some of the glutes exercise to get up to 20kg and still using 3.5 at times (bloody rear delt flyes!)
I've got adjustable dumbbells, which are not for everyone but I love mine.
In short I think you'll be fine with the weights you've got for while. But it's very addictive 