You can reapply anytime when you think you can address issues raised on refusal letter, Appealing decision involve all the way to judicial review, that’ll be question of how VO intepreted and applied the law/guidelines. If rule is in your favor, you’ll go through settlement. Takes time and money to pay lawyer in Canada to file for you.
Now because you mentioned about sufficient funds, what do you mean by sufficient? In your situation it is 1 year tuition fee+ $10,000 cost of living (YOU) + 4,000 first family member + 3,000 second accompanying. I did not include your spouse if you have one. In some situation, they may go beyond that and include things like cost accomodation for a family, daycare if minor etc. If you meet that, then you have one concern out of the way, second will be “ intention of returning back after studies”