I think just learning cranks you should stick to shallow and mid depth divers say down to 8' and no deeper than 10'. By using shallow cranks it will give you an idea of how they feel when you hit bottom and what it feels like when a fish hits and it is also much easier to learn what triggers strikes by fishing shallow and medium divers. The square bill cranks are designed to be fished fast and deflect off cover while the round lip is meant to dig deep to not only help get the bait down fast but also skip along the bottom without hanging up. For 5 good solid baits I think you need to have at least one super shallow bait so get a Manns baby 1 minus, Rapala DT Fat 1, or a Bandit Footloose, then get yourself 2 square bills like the Strike King KVD 1.5, Cotton Cordell Big O, or the Rapala DT Fat 3. The other 2 you want to get will be medium divers, a Rapala DT 6, Strike King series 3, or a Bandit 200 series, any two of those will be good and that will give you a good start to learn and catch fish while doing so.