There is a small addon which tells you how much mana you saved and the MP5 after combat (I usually sit at +2k mp5 from the meta gem):
http://www.curse.com/addons/wow/lmgeffective
if you got the Weak Aura addon it is pretty simple to make it clear when it procs.
WA string you can import:
Code:
dyJMbaGEKq7sKSnbMPiL5IKmBsUjIW3KKDIQ2lSBk2pIOFIe8xu43egkIudgrXWPKJHW5qrlusTuevTyKILRK hIk9uvltqpNQUnkzQcnzPmDfxeP0RrQ8mr56KQnIu1JvQnlQ2oIstJuoTu9zk13rIomvUKivJgrLXJi5Ks4wi PUgQ48OuJtIUmrdtedceXDiIb3JtKslvvkM4SWB4neXZfM5DkkbFOgER7Tuo2FCB684PBHVfkXcrWRb6ld0cy sqeewsOvwLfGCQ5OHbxjCneXxcLerCw6QPJigm46EjJTGfnUb1yWxs7UWezBjX7BHbFwDBB5crCVLuPkA4ezv HAv4cknuWOyJACDVKH3sQufnuJNRRu(TZGAm4o9raAW7n80K2stJKKHlxCJoR4QBBlxEWtG36ElLJDXwyWlmJ CL72sQk2cJNQBjvkgNCUMGsgKWzC16ldUFCB68Kw0ndoxA5J0sE8rsQHRqjwicEcWNa(mqpNSGsMmRctcldds sYqo1C4GbdozbpHwscgaa