Personally I do;
ot think that the Empire is the most open to color schemes and theme. No army really stands out in that area because it's the owners imagination that determines the limits.
Now you said you won't have alot of money to spend and so it will take awhile to build up your army (I hear ya there) and so are wondering which armies can work at smaller games. Well Usually the armies that do better in smaller numbers (in my experience but I haven't played alot of
WHFB under the new rules so this may not be entirely accurate and is just based off of my 10 years of gaming before hand) are Dwarfs, a Warrior of Chaos army (with few marauders) and Ogres.
Dwarfs are slow but can be a tough nut to crack if used right and they can be more challanging in terms of tactics then one might think. They have amazing warmachines and their troops are usually hard to break and can hold there own against most units plus with how selecting your units is done by percentages now Dwarfs have rock hard lord and hero choices.
Warriors of Chaos used to be the best fighters in the game (infantry) hands down but I don't know much about daemons so they may have taken over. The only other unit that can come close that I know of are Lizardmen Saurus. The army itself can have a HUGE variety of units and the conversion/painting possibilities are endless plus they have some of the best models
IMHO (points to the new plastic
DP). Now they also have the ability to be a horde army in that instead of taking actual Warriors you can take Marauders. There is also the Hell Cannon which is a monster and a warmachine. Ever imagine firing a gun and then it turns around and eats you?
Ogres are an army of monsters plain and simple, they could use a new codex but with the new rules they got a good number of boosts. They are a very fast army that can reach the enemy quickly and pretty much your entire army (besides goblins) has 3 wounds and deals impact hits. That being said an Ogre army will usually be outnumbered, there is no way around that. I think I've only seen 1 game where an army was smaller then the Ogres and that was because it was another even smaller ogre army. Ogre magic has a benefit that it dosen't follow the rules for casting like other armies but with the low casting value of Ogre spells they're pretty easy to dispell.
Now what was said about the Empire above being the most versatile army is absolutly true like the Dwarfs they can have an amazing gun line and great war machines but they are also faster and can use magic and
cc units etc. They also have a great variety of models like Wizards, Generals, State Troops, Broad Swords, Flagellants etc.
Skaven are a hot choice right now with all of their new models and the update to the codex plus they are a pretty good force. The current rules emphasize larger games and Skaven being a horde army can field ALOT of units in those games and these units are usually pretty good at what they do. They are also one of the few armies where you can kill your own troops and so you can come up with some very clever tactics especially using slaves.
I don't know alot about High Elves but I do know that they have some pretty good magic and that their units that have great weapons are INSANE. They also have some very crisp looking models such as the new Noble riding a Griffon from the starter set. That's about all I can say there
Now above you said Tomb Knights
I think you ment Tomb Kings. I personally love this army and as the rules stand now their only real advantage is their magic which like the Ogres dosen't follow the same rules for casting as everyone else. Personally I would wait to do this army if you decide to 1 because the codex needs to be updated (and is rumored to have this happen soonish) 2. Because besides magic the
Tk got nerfed in this addition of rules, there are still playable lists but they aren't at the head of the pack in terms out power. And 3 the army needs new models, admitidly for having most of their unit choices made of metal they have AMAZING looking models. But with rumors flying that an update is on it's way and new plastic models are replacing old metal ones it would be a waste to run out and buy the existing models for newer (hopefully better) looking models to come out.
And then there are O&G, O&G are like the Skaven in that they are a horde army and so can fit alot of models in lower points games. They are like Warriors of Chaos in that they have good
cc units and have a huge variety of unit choices. O&G armies tend to focus more on
cc then shooting but they still are able to put out an impressive number of shots from various weapons and in my opinion are one of the funnest armies to play simply because of the sheer amount of what could go wrong makes for some awesome moments
plus the O&G are supposed to be the next codex which comes out although they probably won't get alot of new models as they have some great ones already.
Now after addressing the armies you listed I'm going to suggest my main army which are Lizardmen. The Lizardmen have the best magic in the game (their leaders helped create the world), the 2nd best infantry, a good variety of exotic units and some great models. The Lizardmen being reptiles have a leadership based rule that can make them very hard to break (trust me, Vampire Counts players hated me before the nurfs to Fear and Terror).
Besides having great magic casters who can cast their spells while in
cc they also have Saurus heros who can ride the
WHFB equivelant of a T-rex, now most armies now would be leary about taking things such as dragons and such as mounts but
IMHO the Lizardmen are one of the remaining armies that can still get away with it plus it is an awesome
cc monster and a great looking model.
Then you have skinks, these little lizards can either be made as a horde army in themselves or as support for your Saurus. Personally I use them as support as I see one of their greatest abilities being their mobility combined with their poisoned blow guns. I have used those little guys to kill everything from Daemon Princes to Giants (alive and undead) and Dragons.
Now I mentioned the exotic units. Instead of war machines Lizardmen use dinosaurs and the Salamander has arguably one of the best flame template attacks in the game. They have great giant triceratops that used to be army breakers but they are still usefull and have a number of roles be it a mount for a skink character (or a specific slann), a tank with either a giant blow gun or bow on the back or a mobile platform that provides magic support. The Kroxigors are hulking brutes who serve the same role as minotaurs, ushabti, ogres etc and are also fairly fast. There is also a saurus cavalry that ride raptors but cavalry isn't that great of a choice anymore except for a few armies.
Personally the Lizardmen have always been amongst the best armies to me and so I always have to reccomend them. Now every army can be done to fit almost every theme you could think of, the Empire and Elves are constantly sending expiditions across the Old World. Ogres are mercenaries who fight anywhere at any time. Chaos is litterally everywhere which is the same for O&G. Lizardmen can travel through vast portals and they have ancient cut off cities scattered through the globe. Dwarfs will go just about anywhere in search of gold. The Skaven empire litterally stretches across the planet it's just under ground and Tomb Kings have great undead fleets plus nothing says they have to be from Khemri (aztecs from Lustria, chinese mummies from Cathay or burial mound lords from the Old World). So if you find you like a certain theme or region you can make just about any army come from it or represent it.
in fact I only heard that they exist 
but I 'am planning to drug in one or two players 
(Dwarfs... sigh..)
