I personally think you can learn as many tricks as you want ... to know the secret but don't perform it yet. Let's say you learn 20 tricks, if you are starting in card magic, practice tricks that are easy but hits hard like 2 card monte or a simple transpo in the hand until you get them just right and then continue practicing the other tricks and when you think it looks good and clean, go out and perform it ...
I have to STRONGLY disagree. It is not a good idea to learn all the secrets first. Once you learn the secret, the desire is to find out the next secret and then the next and so on. After a while you know a lot of secrets but are unable to perform any effects. Also, do not try to learn 20 effects at the same time. You will end up mastering none of those effects.
My advice is to start with one effect. Learn the slights and the sequence. After you have the slights and sequence learned, put it together and practice the slights in sequence. When you can do the slights in the proper sequence without looking at your hands, then script out your patter (what you are going to say during the effect). Then rehearse the slights, in sequence, with the patter until you feel completely comfortable with performing the effect. As you are doing that last step, then, and only then, move on to learning the slights and sequence for the next effect. After you master three effects, go out and perform.
I say rather than tricks, you should start with sleights first. Learn and practice your sleights and then go on to make your own tricks. You'll be surprised with what you can come up with on your own. Or if you want to go with some gimmicks, buy a gimmick and (I know people are going to get their pitchforks ready for this) don't read the instructions. Instead, see what you can come up with on your own and go from there. After all, the easiest things to practice are the things you come up with. At least I like to think so. Good luck!
Again, I disagree. There is nothing wrong with learning slights, but there is little motivation to learn a slight if you don't have an effect in which you can use that slight. That is why books like Royal Road and Card College go over the slights and then teach effects that use the slights and why videos and some books teach the slights in the context of effects.
An added benefit to learning effects that use the slights is that you develop the ability to use the slights in sequence. That is, you never just take a deck and do a double lift or just do a pass. There usually is something that happens before the slight and something that happens after. By learning the slights in context of the effects you learn how to do get into and out of the slights more smoothly.
Finally, for an absolute beginner, it really doesn't make sense to try and come up with you own effects. At that point in your development as a magician, you don't have a good sense of how to structure an effect. I think the OP would be better off learning the effects on the DVDs one at a time, practicing them, rehearsing them with patter and then performing them.
Learn effects that have stood the test of time. There is a reason that those effects are considered classics. While learning and performing those effects think about what makes them work. Think about how they are structured and look at them from the spectator's point of view. Only after you have figured out what makes other people's effects work do you really have the knowledge to structure your own effects.