What's the basic knowledge level or basic amount of education you need to be a successful graphic designer?

If you’re going into business for yourself, then you can bypass college and just work your ass off on Adobe Photoshop, InDesign and Illustrator. I will stress the “work your ass off” part of that scenario.

If you are ever thinking about looking for a graphic design job at someone else’s company, you should really consider a college degree. It’s a very competitive field.
You will absolutely learn some good things about graphic design in college.
Possibly one of the most valuable things about being in college is being in a ciriculum with a group of your peers. In that sort of environment, everyone’s creativity feeds off everyone else’s and it can become a very powerful and motivating factor in taking your work to the next level.

A home based graphic design business is not a good idea. Many out of work but well experienced graphic designers have failed in that area even with their experience and networked contacts. Most companies who need the services of a design studio will only approach those with a history and a reasonably large staff. One man shows are not favoured. My wife is the General Manager of a very successful graphic design and publishing company, they have literally hundreds of Gold and Silver Awards over the past fifteen years from all manner of sources, and they are feeling the downtown in business at the moment. All of her staff have multiple degrees associated with the industry.

I have seen autodidactic (self-taught) graphic designers take three or four times as long to produce an inferior result to an in-house professional. It isn’t as easy as it looks. You need a working relationship with some print houses, you need to be able to proof stuff off the press and sign off on it, you really need to know what you are doing. Mess up a print run and you will lose thousands of dollars.

You can find a community college program that should only be a few years. Some universities/colleges offer more intensive programs. But having the knowledge and having the clients are two completely different things.

Honestly, you will not be successful with a home based graphic design business, certainly not so in the current economic situation where almost all advertising and marketing budgets have been slashed. Even with the education, you need to get the clients, and no one will be running to the door of a recent grad with no real life experience. Not to mention you are competing against huge graphic design agencies who have cumulatively tens of thousands of hours of experience, a portfolio that reaches the moon, and hundreds of clients.

If you were determined to do this yourself though, I would recommend the highest level of training you can find, university would be good. Or you could take multiple college courses. Graphic design is not a job but a field and there are many subfields including print design, web graphic design, etc, all of which have education specific to themselves. After graduation, I would recommend becoming an apprentice or working in an agency for a few years so that you gain all the actual world knowledge you need (cause university doesn’t teach that). THEN you can go freelance. Yes, it’s a lot of work, and a lot of time.

You CANNOT bypass education and simply work your ass off learning the programs. You. Will. Fail. You will eventually fuck up something you didn’t know about because you weren’t educated, and your reputation will likely be permanently ruined.

Web design is much easier to learn on your own, but even then education is appreciated.