Corns and Kings are wonderful: I highly recommend both for a starter herp. Easy to keep, easy to feed, and most are very well mannered and calm with handling.
BCI: "boa constrictor imperator" (boas). The most common BCI boas in the hobby are Colombians, in which females will most likely need a 4-6 foot cage and males 4'. Hog Island BCI boas are considered dwarf boas and should stay on the smaller side: some keep these and central american dwarf and mexican dwarf boas in tubs without issue.
Cresties are great but can't tolerate higher temperatures.