my biggest advice to you... not quantity, but quality.
This does not mean perfect technique, this does not mean the most popular tricks on the market. What this means is, ask yourself, "have I perfected this effect to the best of my ability." Again, this doest NOT just mean technique.
20-25 minutes... you would be surprised how fast this goes by in a real performance.
With the right patter, the right amount of interaction with your spectators, and with well-placed pauses before a trick's climax, you can easily, yes, EASILY, fill a 20-25 min slot with 4 effects.
What this means is... you can carry with you only a single deck of cards, and blow away a crowd of 5-10 people for 20-25 minutes, doing 4 -5 effects with a single deck of cards.
How do you do this? well, with practice, critique, and with learning how to read people and learning what your style is.
First, start by choosing tricks with similar or slightly similar effects. An ACR moving into coins and flash paper and appearing wine bottles... yeah, not so natural. An ACR flowing into a production of the four of a kind of the selected card, then into a trick with a 4 of a kind (waving the Aces? etc...) is very natural.
Now, once you get down 2-3 tricks that flow naturally and quickly together... all you need is an opener and closer. Both your opener and closer can take time because you have to explain them, and link them to the middle section. Rarely you will see a magician do their opener, and quickly move into the middle section of his or her performance, because you need to give the opener time to set in and let the audience absorb the effect. If you dont, they will either forget the opener, or they will still be so caught up on it, they wont fully enjoy the middle of the routine.
For an opener, you can do something so simple as a coin production. Learn your classic palms, learn various vanishes and productions, use them, show off your skill. This can last anywhere from 1-4 minutes.
As a closer, choose something you are comfortable doing, and present it in a way your audience KNOWS it's the end. THis is a BIG mistake many magicians make. They will do a common closer (card to mouth, card to wallet, etc...) but their presentation doesnt FEEL like a finish. You have to work on this.
I hope this helps.
In summary, not quanity, quality. Quality = rehearsed and critiqued solid routines WITH patter, and at a relaxed pace. Let your audience fully experience and absorb your effects. Speed hurts you in the long run.
