Getting started is not that difficult. Ultimately, the biggest investment is just the learning curve that you have to go through. Now I use a pressure pot (I think about $75 at Harbor Freight) and it has definitely improved the quality of my cast parts but I worked without it for a couple years and it's not needed before you're comfortable with the basics.
I recommend using Smooth-On's Oomoo silicone because it's a simple 1:1 mix by volume - no fancy scales needed. I like the Oomoo 30 but it comes in different formulas with different setting times and hardnesses - your pick. Their Smooth-Cast 305 is my resin of choice and it gives you a lot more working time than Alumilite. That's especially nice when you're in the early learning phase.
The actual use of resin and silicone isn't so hard to learn. The real learning is the mold construction. I should put up some kind of tutorial I guess. There's probably lots of different ways to do it and mine might not be the best but the process seems to go real smoothly now and when I started I was REALLY clueless. Believe me, if I learned it you can too!