Doing more than 5G requires substantially different equipment (IE more expensive except perhaps the keggie), much more dedicated space and quite a lot more planning. I would seriously consider starting out at 5G batches and adding equipment as you see fit.
Personally my favorite items are the grain mill, immersion cooler, stir plate, and immersion cooler. You should have a ton of equipment before attempting a 10G batch. The starters need to be twice as big if not bigger, the weight of the pot is too heavy to lift 12G at 7lb per gallon is about what... 84lb, you need to plan a tired system to avoid moving stuff once it's filled up, several propain burners since you don't have an insulated MLT and you need to heat up water.... really this is a ton of equipment and space.
I would get a nice large pot, I love my 42qt and I would go with SS instead of aluminum. If you upgrade, you can still use this for things like heating up water instead of a kettle. I would get a round cooler with a braid and eventually upgrade to a manifold. You NEED a cooling system, either immersion or hop back or chilling plates. You should get a stir plate and a nice grain mill (rollers which are adjustable). Both will be used when you upgrade to 10G so there is no money wasted.
Also start out small with all grain, get the process down well and read. You are getting into something that is wonderful but you should know why stuff happens and what makes stuff work, reading books is the only way to do that. The forums take you so far.
You should make the switch to AG though, it's cheaper and you get much better beer but start out with 5G and simple beers like IPAs, porters, stouts, single infusion beers.
The immersion chiller, nice pot, grain mill and stir plate will run quite a lot of money... like about 600$. All of these can be used in larger batches of beer. Honestly I have been doing this for about 5 years now and I have never had a problem with 5G batches, I don't split it with friends but showing up with a case of beer is awesome, esp when it costs about 12$ to make it.