The cash shop is a little disappointing sometimes for those that wont/cant afford/dislike using it. My best advice is to lvl ONE set of gear for your chars meaning gloves,boots,helmet,belt and using warehouse to go between chars. This will help with saving rupees. Only get and use chips when farming or for dungeon parties. Sell all your crap
My fiance forgets to sell her stuff an just tosses it in wh, I made her clean it out yesterday and she made 9 mil off just r2/r3 pots/scrolls and gear she didn't need.
When you buy something, thing about if you really need it... Sell cards and other items in auction house on the weekends. It seems like people buy faster and pay more on weekends. Check prices so you don't get gouged or price cut. You may find a sweet deal. IE: today I bought a logsplit card from auction house for 150k, I can resell easily for 1.5 mil and that would be selling cheap on Yeti.
Bottom line... be a cheapskate! I went from 5k or so rups in wh to having 20mil at least being a cheapskate and re-using gear.
The above tactic is why I have CS items on my chars... save the money an buy the item in game. Your not out $$$ and you bought the item already +4ed.