Two kinds of progress. Your kit levels in the Frontier. Your rank climbs from XP earned across the network. Neither is for sale.
Your rank shows as a prefix in chat and on the tab list, network-wide. It's based on total XP.
Crucible matches: kills, how far you get, and wins. Tournament wins pay the most. XP is shared across every server on the network, so it follows you.
Some things earn a title you can wear instead of your rank prefix: winning the weekly tournament, your faction tag, and others you'll find along the way. /title list in game.
Kits level 1 to 10 in the Frontier by playing them. Rank and kit level are different ladders, and both are earned. The kits.
Paid ranks are cosmetic: a prefix, auras, chat colours, homes. They don't add XP, don't change kit levels and don't change a fight. What each one includes.