Unless you've built-up personal contacts with access to bulk supplies at good prices, you'll always be very hard pushed to find better value than Easy Composites, plus you have the wealth of practical advice available via this forum
If cosmetics aren't overly critical for you, especially if you're in an experimental stage of producing things, then the 'Black Stuff' line of lighter twill sold be EC is probably a good fabric to use until you've got your techniques nailed-down.
For stability and cosmetic finish, the 240g twill sold by EC is probably the best fabric to go for. I'd recommend this over their 'Pro-finish' fabric, despite its' resin-bound nature, as it's drapable, very stable (won't fall apart when handled) and gives the tightly woven look of pre-preg twill. For heavier backing fabrics, there may be other suppliers with deals available on selected fabric weights if you search around a bit