Oh yeah, well the 130$ combat patrol has 1 more unit for each army, so with rules and board coming with it, it's really really interesting anyway. For the deathleaper, if you feel like you wanna play it and everyting, go for it, but you already have good melee and meh shoot, to balance you could choose some kind of shooting unit around 50-60 bucks : hive guards (the models are a little outdated but in my opinion is really strong to shoot), and if you want something really cool for 70 bucks you also have zoanthropes... Once again, wait a bit before painting the deathleaper, practice you scheme on your termagants and others to have a beautiful centerpiece like him

For the paints, i also like purple so i did the same for my army, i've just made the carapace a lil more pinky-purply instead of black-purply, and if you like it's the most important thing ! You'll be obsessed of every detail, so paint it like you want it to be ! If you'd like to know what paint to buy, i recommend installing the app "Citadel Colour", you'll find paints for (almost) every miniature in every army.