This is my traveling speaking kit. This has two speakers, projector, cables and spare bulb inside a Pelican 1650 case with dividers.
Be sure you have the best quality you can afford. You would hate to continue to tell the audience if you could just see it on my screen you would appreciate it much better or if we had some speakers you could here this a lot better.
If you are a camera club invest in a kit that you use to show your members work. If you speak to groups always carry your own kit just in case the place you are speaking isn't prepared or has an inferior projector or sound system.
I use two of the Roland CUBE CM-30 speakers [$219]. This lets me have stereo sound out of the sound system.
I have a 1/4" jack running out of one into the other one. I have the audio from the computer running into the Aux 1 jacks for Left & Right.
I can project my voice pretty well, but if it is needed I plug my Shure Wireless Lavalier into Channel one and can now also project my voice if needed.
My Shure FP Wireless Bodypack system.
I have an older Panasonic projector [Panasonic PT-LB20VU Projector] that works well. I recommend at least 2000 lumens for light output, unless you are projecting to 10 - 12 people in a very small dark room. Expect to pay between $500 to $1000 for a decent projector.
Here is a link to a collection that might work for your needs here.
For a screen, well this varies a great deal depending on where I am speaking. I have used 11' seamless paper, white walls, large screens and often will carry my 5'x7' fold up white/black background.