I apologize in advance for this loooong post, I didn't mean to make a subpar essay >.>
I'll try to remember posting something from our Mindcrack server (pics) when I get home... For our map we spent a majority of our first day finding a scenic spot a good distance away from the initial spawnpoint (some multiplayer seclusion is nice). We made our basic homes and whatnot, and as soon as we had a better form of travel, me and my 2 friends searched the world for a good combination of things that would make for a great communal area with room for expansion and personal homes nearby. We found a nice mountain with a large cliff face, in between 2 oceans and large mountain islands with all sorts of other stuff I could go on listing. We ended up making a "common" area, where we set up most of our supplies, power generation, spawners, farms etc. This place was intended to be our stepping stone towards making our own awesome places soon after.
I'm a fan of elevated homes with scenic views, so I started off with a small shack to get some basic things going (power generation / storage, ore processing, manual farms, etc...). As soon as able, the 3 of us had our basic electric jetpacks to help us find an even better place (we were originally in a desert which limited many of our forestry plans, but it looked nice). It was then when the 3 of us put our resources together that we were able to get this big elevated complex going, with me focusing on expanding the common area, one friend focusing on bees (they can get pretty complicated and demanding of your time), and the other on tree breeding / thaumcraft. I have to admit, by yourself there is a daunting amount of things for you to get into and keep you occupied....the best you can do is research what's available in your modpack, research other people's designs or real world designs for homes, and make it mesh together so that form goes with function. I have a habit of making large decorated rooms, and then deciding what's going to go in there. It's worked out for me so far, but other's like to build their homes around their machines. I also like showing off the machines instead of hiding them in a basement, so just figure out if you want to have an open area with access to various things, or separate rooms of this and that...
I would recommend doing some exploration as well, we had some big boosts to our early productivity when we found things like thaumcraft tools and portalguns throughout our travels. OH also as soon as possible we worked on getting a soul forge going to start collecting soul shards. If you have soul shards activated I strongly suggest making various types of spawners, as they can be some of the best ways of obtaining mats to the point that you're doing less "farming" and more building. Spawners can be pretty fun too, since there are many creative ways to make them look cool and work effectively...i.e., endermen / creeper spawner with quicksand, blaze spawner w/ water, firebat spawner w/ tesla coils, exp farms w/ skeletons / zombies that take fall damage and are killed manually, or eventually through upgraded golems... Let's not forget the fun farm animal processing systems you could come up with using pistons, those fire spewing blocks, water, quicksand, sentry guns, deployers...oh man the possibilities... And those farm animals aren't just food sources, since what they provide could be valuable for energy and magic (most meats can be turned into methane, leather / feathers for thaumcraft aspects).
Although not totally necessary (but fun), you can eventually look into thaumcraft. Just be aware that it can get expensive if you don't have a solid research area set up, and a good collection of research mats stockpiled. Thaumcraft research can be very heavily influenced by what you have around your research tables, which can lead to some fairly awesome looking magic areas for those that are aware of that aspect. Someone had a forum post about that someplace that really helped, something about boosting Thaumcraft 3 research efficiency. I know my area took a good amount of materials to set up, but when I started my research, man it proved worthwhile. Some of those aspects just shot up, whereas on our last map with a lone research table we were literally burning through materials. I also played it smart and made my magic area faaaar away from our common area, which kept our main area's flux levels relatively stable.
I dunno, lots of stuff to do and everyone plays differently. I don't usually go in with a solid plan and just build and expand as the need arises... I don't like to hide too much cause I like to get to the point where I can show off a structure and help out newer players when possible. Therefore, having a hidden cave / areas isn't usually one of my goals for a home.