Do you think a DEMB Classic Flip-It ( http://www.dembflashproducts.com/flipit/ ) and basic diffuser ( http://www.bhphotovideo.com/c/product/407175-REG/Sto_Fen_OM_EW_OM_EW_Omni_Bounce_for_Canon.html ) can get most of it done?
I think you can go two ways... either OVER THE TOP (like surapon) or KEEP IT SIMPLE (like the quote above).
I prefer to keep it simple, esp starting out and when you are on a budget. It takes courage and self confidence to shoot pictures of people and surapon is probably the most confident and courageous photographer on the forum!! (Not to mention, as everyone here will agree, surapon possesses exceptional physical strength, stamina and mental fortitude! Just look at some of his equipment carrying posts!)
There are a LOT of flash modifiers and accessories available. It's a HUGE BUSINESS, the business of flash accessories. It's easy to spend a lot of money on flash stuff!! Start out with the basics.
I think that based on where you appear to be in photography, you should buy the Sto-Fen modifier linked above for sure. Every photographer owns one and likely uses it for years and years regardless of what else they have and use. It works great, it's inexpensive, unobtrusive and doesn't take up a lot of room or add weight.
The next thing you should consider is a FLASH BRACKET. When you elevate the flash, you will drop the shadows behind the subjects and greatly improve your shots. I use this one because it's very well made but still folds down easily for storage. If you get a flash bracket, you will also need a off-camera flash cable.
If you end up doing the flash bracket, you might also consider rigging it up to be able to easily remove the flash and hold it to the side for more versatility. (Just a thought.)
Only after you have these items, should you consider buying more sophisticated flash modifiers. I own a Gary Fong Lightsphere and few Lumiquest items but the StoFen stays on my flash 90% of the time. You may find that you can build your own modifiers and save a lot of money. Photographers have been using white (or amber or green) 3x5 index cards and rubber bands for decades! I also suggest you read David Hobby's Strobist Blog for more ideas. He's a master at flash and often uses cheaper manual flashes and hand made modifiers.
Let us know what you decide!