I guess first of all when you say "starter net" are you talking about something inexpensive to start with ? or do you mean something with a smaller diameter that would be easier to learn to throw?
the other consdieration is your statement that you are going to try to catch bait at cumberland next week. catching alewives on cumberland this time of year is very difficult to say the least, the bait is very deep. it takes a pretty good net to stay open until it reaches those depths , yet sink fast enough to actually "trap" bait as it passes through the level where they are. usually starter nets arent a viable, consistent option this time of year for alewives.
another suggestion is to go ahead and spend the money on a quality net with a sufficent diameter to catch bait in all situations, whether it be deep or shallow. a couple of very good nets to consider would be "calusa nets" (in my opinion the best all around high quality net), second would be a "baitbuster net", (also very good nets, especially for deep water, they sink like a rock) and another is a "cracker net" ( a cheaper version of the calusa, but still a very effective net).
catching deep bait is also going to require some diameter, i along with dozens of other bait catcher including most of the guide services throw a 20 foot diameter net. this larger diameter is also good for catching shallow gizzards as the have a hard time outrunning the edge of the net before it catches them.
if you go ahead and get the correct net to begin with you will be ahead of the game and avoid throwing the wrong net that doesnt catch bait and wastes alot your time. you will utlimately put that net away and end up buying what you should have bought in the first place.
if you are concerned about learning to throw a large net , dont be , i will be more than happy to show you how to open the net , just pm me.
any way you go i wish you the best of luck....youre going to need it lol, shad do not play by the rules