Can I have two rune up, one exhausted one ready, can I tap the ready one to ready the exhausted one?

No, you cannot tap (exhaust) a ready rune to ready an exhausted rune.

According to Rule 415.1 and Rule 414.1, Ready and Exhaust are states that mark a card's availability. There is no general game rule that allows you to "tap" or exhaust one rune to ready another.

To ready an exhausted rune, you must use a specific card ability or game effect that explicitly instructs you to "ready a rune" or "ready an exhausted rune." For example, some cards may have abilities that trigger or are activated to provide a "ready" effect. If you simply exhaust a rune, it only adds 1 energy to your pool (per Rule 163.2.a), and the rune remains exhausted until your next Beginning Phase (Rule 315.1.b) or until a card effect readies it for you.