I disagree. While ranked can be great, it's designed for truly competitive play and see how you measure up against others. Normals is still competitive, but designed for fun and practice. Which one you play is more of a function of what you want to do with the game.
That said, if you just reached 30 then you'll likely be placed in low bronze just based solely on not having the experience to know what to do in a competitive arena in the game. Don't get discouraged if that's the case. You will be playing against people in their best roles and champs that have been playing much longer than you. You will (eventually) be playing with people of similar skill and against similar skill. And you'll have trolls and smurfs all over the place.
That said, there is definitely the opportunity to learn from ranked. I suggest using op.gg or replay.gg to record your matches (the latter will record all matches automatically) and use them often to see what you are doing right and wrong. Little improvements go a long way.