Build your own Minecraft economy plugin: currency, shop, auction house, jobs and salaries. Describe it in plain English, get a compiled .jar to test.
An economy plugin comes down to four parts: a currency with a balance per player, a shop to buy and sell items, an auction house for player-to-player trade, and jobs that pay out. Describe those parts in plain English, and Minax writes the Java, compiles a .jar, and lets you test it in game first.
It depends on what you actually want. The well-known ones are solid, but you inherit their commands, messages and balancing, and you usually have to stack several plugins to get currency, shops and jobs together. Generating your own gives you one plugin that does exactly what you described, with your names and your prices.
You need an economy plugin that keeps a balance per player, plus a staff command to credit an account. Ask for that command explicitly in your prompt, along with the permission node that guards it, otherwise anyone on the server can pay themselves.
Not required, but useful. Vault is the standard middle layer between plugins: your economy registers as the provider, and other plugins read balances through it without knowing your code. If you want that compatibility, put it in your prompt and install Vault on the server. A self-contained economy works fine too.