Most of these are good.
I'd hazard that
is (IMO) super dull to play. He is probably, by far, the easiest jungle champion to learn, since he has amazing sustain and his kit is extremely straightforward. However, the straightforwardness of his kit also makes him less than stimulating. On the other hand, he's pretty cheap, so go ahead and pick him up if you'd like to give him a try.
is another good one. For a newer player, I'd pick him over
, since his ult is much more forgiving to use (i.e. if you whiff a Sejuani ult, you may well throw the fight; it's pretty well impossible to miss an Amumu ult though). Both have similar kits and fill very similar roles.