Every member needs to own a professional-quality instrument before you play live gigs. Choose your gear carefully, buying instruments that complement the style of music you play. A guitar with a great sound for Chicago blues may not give you the brittle, crunching sound you need if you play metal or hardcore.
Your PA system is as vital during practice as live performance, because you need to know how every instrument sounds in the finished mix and make necessary adjustments before performing live. Your PA system has to allow your singer's vocals and every musician's instrument to be clearly heard.
You can start recording demos and promotional singles by connecting your PA's mixing board to your computer. Recording software is relatively inexpensive and most developers offer demo versions.