If I failed to get Mbbs seat in merit 2018 could I spend 1 year for studying to get MBBS in 2019?? Somebody saying that It is waste???

It purely depends upon you. Don't listen to anybody rather than listening to you. Because its only you who will study and work hard. If you think you could do it, then go all the way. If you think you are not prepared enough for handling such things then don't waste your time in preparation. Just ask yourself. It could be your life changing desicion. So think wisely.
I would suggest you to prepare for neet ug 2019.

Good luck..

Hey Sarvan,
From my Point of view, its never a waste of time, if you a hard working and dedicated enough towards your goals.
Well, it was my own story. In my first attempt I got 398 marks, which was not enough to grab a seat at government medical college. Then i took one year of drop and finally got 617. So it depends how one utilities it's time. You need to be consistent towards your studies in that particular period of preparations. But well, this is not the right time to think over it, you must concentrate on this year's exam. Hopefully you score good.
Good luck