In the case I want to say there is a lot of things available and implies 'the more the better', which word should I use?
This is difficult to answer without you providing a clearer idea of the situation. That said, I shall take a stab at this anyway.
Abundant implies that there is more than enough and greater than merely sufficient.
Both sufficient and enough imply that the quantity satisfies the need and don't necessarily provide any more information.
If I had to select one of these words to answer your question I would use abundant. The reasoning behind this is that you want it to imply 'the more the better,' and neither 'enough' nor 'sufficient' have that connotation. In fact they have the opposite. Imagine a store owner describing his vast selection of fruits; which of these sounds better?
"We have enough variety", "Our variety is sufficient", or "We have an abundance of different fruits."