Use your first moves to either make three-candy matches against the meringues at the bottom, or free up the jelly coated striped candy up the top. Ideally, your two striped candy will be the same colour, so you can use a colour bomb to detonate them later on. Once they have been set off, provided you kept them in the same column, it will free up the marmalade on the wrapped candy in the bottom corners. Any other wrapped candy you can make will help you crush through those meringues.
You are relying heavily on special candy to beat this level, The chameleon candy will make lining up special candy difficult, but not impossible. If you get the pattern for a four-candy match with a chameleon candy in the middle, leave it in place if you can whilst you make moves elsewhere, and the chameleon candy will eventually change colour and automatically make the special candy for you.
On level 307 you have 40 moves to clear the jelly which is all in the bottom board. At the top are two smaller boards. The lower board has four layered meringue blockers on the bottom and sides with a wrapped candy under marmalade in each corner. The top two boards have a vertical striped candy in each top far corner. To make things even more tricky, many of the candies on the lower board are rainbow candies which means they change color every move, making it harder to set up matches.
It is worth working away at breaking the meringue blockers because there is jelly under them. Having some well placed vertical and horizontal striped candies can help with this. A striped and wrapped combination can also be extremely useful too. A color bomb and stripe combination could be useful as well. Do not worry about removing the main area of jelly, this will pretty much remove itself as you work away at the blockers. Without removing those, you cannot win anyway so there is little point in worrying about them until the end. The top boards could be used for making special candies but apart from that, they are not that useful.
At the beginning on level 307 you have the choice of a jelly fish, color bomb or striped and wrapped candy booster. There may or may not be useful, depending on where they are placed and how well you do. It is rather a risk using them. You may find that the same applied to the in play boosters as well.