What will be the linking theory to a eCommerce site?

[avinash]

Look!! I can say you any number and you may take it also. But the main fact here is that the number (the budget) has to fit into the profile and competition of the product's keyword. To get a sale you don't have to outbid your competitors necessarily.

And its preferable that you choose a single product or group or platform which can be easily targeted and also achieved. Its not like that as you are targeting so your competitors must not get sales, yes they will get but you will get sales too.