which falsh gun would u recomend me??
Any flash that has a Guide Number of 35 or higher, conforms to 'standard' ISO hotshoe specs (Olympus, Canon, Nikon complies, Sony/Konica-Minolta does not), has 'auto' modes that work at various f-stop settings (f/2 till f/8 @ ISO100, for example), has manual override for flash power output (termed 'power ratio' control), and has a tiltable (up/down turning) and swivel-capable (left-right turning) head, are the minimum features you'll need to get started. Zoomable flash heads (has fresnel lens to focus the flash to match lens' longer focal length), slave trigger sensor, and a socket for sync cables are a bonus. Here is a shot of my 383's ancient analogue control panel on its back:
The ISO/ASA, F/stop and meter/feet range guides work in tandem and is just an adjustible visual reference scale that helps you determine if your manual or auto setting will give a correct exposure, but otherwise does not set the flash output. The green 'A' is the lowest f-stop auto mode (ie. lowest threshold of light output) and can be switched to f/4 and f/8 (corresponding to ISO100) if you need to work at higher f-stops with your lens. The 'full 1/2 1/4 1/8 1/16' scale is the power ratio control for you to use in manual mode, where the flash ignores its light sensor reading and relies solely on this scale's setting.
Having said this, the only flash I own that has these features and have used is my Sunpak 383 which is hard to find in Singapore. The newer, Sunpak 5000AF should be better a bit, having finer digital controls through a LCD panel and zoomable head, and I was told by Sunpak Japan that the Nikon-mount version of it should work with my Olympus E-330. But for you, a Canon user, it's TTL compatible! (not sure i-TTL or E-TTL).