Its fine and almost everyone does it when the hit 30 these days. Some guys want to get all the champs so they never really git hit by this, while other people like to just play a core group of champs and their pools grow slower. I hit 30 with a group of friends and over half of us all talk about hitting the minimum champ restriction and just spamming some cheap guys to play some rank. Lets be real, would you be a better player if you could play any role with 5 or six different champs each, yes, but you can get by just playing 3 or 5 guys and avoiding some lanes. Shock of shock the new champ select pick your lane before queuing is there to support just running down one or two roles/lanes. As the player progress though time their pool will grow and so will their experience with the game by playing rank and that is part of ranking up learning that maybe spamming one champ is not great in all comps. Just let people, do what do, and if they fail into low silver or bronze, just remember that is why its there, to be the bottom of the stack to show that you are not doing something right and maybe expanding your pool might help. Furthermore the entire question is baseless as how would you ever discourage this, set a total cost minimum restriction to enter rank, I can just here the cries of people complaining about how riot forces them to grind for expense champs just to get into rank "oh I just love playing champ x, y and z why does riot punish me by saying I need to buy some more expense guys". If this is a personal question of should you just fill out your pool and play some rank, then yea, spam some 450 get into rank and have a good time, who cares if you hit that million to one roll where your left with only one or two champs to pick, get some game experience in the more serious "lol" serious side of league. Having the right champion will not save you if your clueless on what to do.