1. Mana Reflection doubles mana. This is not a triggered ability given the word "instead"
2. Selesnya Taps for 4 mana (due to mana reflection's static ability)
3. Mirari's Wake's ability triggers and is put on the stack
If Mirari's Wake resolves appropriately then your mana totals 5.
One correction, Mirari's Wake does not get put on the stack. Mirari's wake's triggered ability triggers off of a mana ability, doesn't target and adds mana to the players mana pool so it too is a mana ability and adds mana to that players pool without using the stack.