Pivx is already over valued if you want it for master node, but the price is fine if you want just few to keep for long term.
If I were you, I would look out for low valued masternode coin with nice project that is still on early development and buy as much as you can before the price spark. OBSIDIAN (ODN) is your best bet. It will be hitting exchanges soon. They will provide android and IOS encrypted messenger with masternode and other nice features still hanging in the roadmap. Check
www.obsidianplatform.com