Just to add a little info to that:

Its always better to buy more weed if you have the money because it will probally save you money in the long run:

If you get Grams for 20 and and Eigth (3.5g) is 50 then for you to buy 3.5 grams for 20 serperatly it would cost you 70 dollars, so by buying an eigth you save 20 dollars...get it?

and as for how you smokit it...just try to grind it up a little in your fingers and put it into your smoking "Device"