Hey dear u yourself have pointed out your weakness.....................just improve them.
Get your concepts cleared in accounts and costing but the question is how. Well the popular opinion would be to practise practise and practise because you refer books of any author he explains his concept only through numerous sum so indirectly they hint that solve all these sums to understand his books right?
Just go throught the pass suggestion and complier throughly for accounts and costing this will help u a lot.
You have said that u have not prepared upto the level required in ca preparation? I think nobody has predefined the level till now for preparation for ca exam. The more you study themore u r prepared so just study study study.... and dont have notion of meeting a imaginary level.
I think u r studying chartered accountancy and accountancy should be a core subject if i am not wrong. so if ur weak in acconunts dont just regred over it and waste time. take one good book like shukla grewal, taxmann and study it throughly one time . You will then realize how easy is it to manage accounts.
As far as costing is concernet well my freind you are not alone.Costiong is titanic of ca course .It drowns along with it many studenst . But life jacket in form of FM is availabe which can help you to cross the waves of difficulties of costing.....in short do Financial Management thrughly.Its very easy and intresting. One more thing the more u disucss your weakness the more weak u become. so start studying instead of discussing weakeess