Mana echoes states:
Whenever a creature comes into play, you may add

to your mana pool for each creature you control that shares a creature type with it.
Mana echoes does
not check the
number of creature types that are shared. There is only one check with two possible answers for every creature you control:
Check: Does this creature share one or more creature type(s) with the creature coming into play.
Answers possible: True / False
The amount of mana you gain is the number of true's you get from appying this check to all creatures in play you control. Remember that your Mistform Ultimus already is in play when this trigger is put on the stack, so the ultimus will yield mana itself (just as a flametongue kavu will kill itself when it is the only creature in play when it comes into play). This is the same as with coat of arms, in that a mistform ultimus will
not gain +2/+2 from a creature with types cleric zombie.
Edit: Remember also, that when gaining mana, it is all or nothing. So you get either zero mana or the maximum amount, you cannot choose a number in between.