Mangrove monitors ( v.indicus) grow to 1.5m. I don't have any experience with these monitors but from what I have heard they are not the easiest monitor to keep.
I would agree with Nalege that ackies would be a good monitor to start with.
Mangroves are a very bad choice for a first monitor; they are extremely flighty, easily stressed animals that have quite specific requirements which if not met, lead to immediate decline in their health.
Of the dwarf monitor species, Gillens, Ackies and even Storrs are great choices. Only get a larger monitor if you're willing to commit a great deal of space, time and effort to the animal.
Regards,
Trent.