Well going for dummy or schooling totally depends on how you are. If you are really very good with your basics i.e, even though you dont have extended knowledge regarding a particular topic, the knowledge you have is clear with an answer to each and every why. If you are good at this it will be very easy for you to learn the upcoming topics but if you are not good at this you must Give your time to it which is possible if you go for schooling as they teach everything with basics plus some are a little cooperative so you can get help form them and besides this youll be moulded to handle everything.
You can go for both parallely if you can handle pressure and the work load.
Goodluck I hope this helps you
It all varies from student to student. Whether the JEE toppers were from dummy schools or not should actually not matter to you because the kind of preparation they were undergoing may be entirely different from you and you just can't compare yourself with anyone.
It is all about your time management skills and how fast and good you can grasp the concept. Whether you have joined a dummy school or not, how many test series you have enrolled yourself for won't actually matter that much in the long run as your dedication, devotion and hard work will
Hope this helps and all the very best to you!