First and Foremost, you should stop playing as a count, it is no longer as straightforward as it used to be. By playing as a weak starting character, you are intentionally handicapping yourself for a game you were completely unprepared for. Try playing as a french duke to begin with. That means that you will have the power of your liege for defensive wars, and can declare war on people much weaker than you, ie rebellious counts and weaker dukes. You should start out only going to war with people who you outnumber by 50 percent, minimum, since you have to deal with seiging and defended bonuses.
You should try not to rely on warfare. Making the right marriage matches and waiting up to an hour for them to come to fruition is part of the game, (playing the long game is part of all paradox games really). In fact, Marriage is actually a much stronger mechanic for taking territory than combat. Not only that, but marriage is the most powerful mechanic in combat as well, because it allows you to call allies with vastly larger militaries than you can command early in the game. An alliance with the king of NearbyNation will let you call in thousands or tens of thousands of additional troops.
Still, the overall point is to stop playing as weak characters. Counts and the occasional 1 province duke in ireland are not advisable start locations for someone unfamiliar with paradox games, because like real life, paradox combat is very swingy. A 20 percent difference in starting numbers can be a 200 percent difference in casualties. That means when starting out, make sure you absolutely have a substantial numerical advantage against whoever you declare war on.
As for your example of losing a battle where you had superior numbers, you probably made a mistake with regards to combat morale, but its difficult to know without screenshots. Even if they had a vastly better general you should not lose a 1000 to 2500 fight, unless you had virtually no morale (probably from not paying the men).
Basic Concepts to Practice:
Revoking a county title as a Duke. This usually starts a war of rebellion that you can crush.
Invading an independent county as a Duke. This includes ones rebelling from their liege that have become independent temporarily
Marrying daughters into a powerful alliance (nearby, but not where you want to expand to)
Marrying sons to inherit land
Keeping your most important vassals and advisors (particularly the spymaster) happy.
This isn't a complete solution.
Launching the game via Steam -> Launcher -> Game appears to do some magic, aka it seems to trigger verification of DLC ownership that launching the game via just ck2game.exe -> Game or just ck2.exe does not.
Regardless, the launcher passes through various parameters to ck2.exe to set which mods to load and which DLCs to exclude:
-mod=mod/[mod name]-exclude_dlc=dlc/[dlc name]
For example, this would theoretically launch the game with 2 mods enabled and 2 DLCs (Russian and Mediterranean Portraits) disabled:
"C:\Programs\Games\Steam\steamapps\common\Crusader Kings II\ck2.exe" -mod=mod/Realign_Celts_Men.mod -mod=mod/Edits.mod -exclude_dlc=dlc/dlc014.dlc -exclude_dlc=dlc/dlc016.dlc
However, knowing this to create a shortcut with these parameters will not work, as it does not invoke the magical Steam fairy that verifies the DLC ownership that allows them to load ingame.
Without that verification, you (mostly) out of luck. There is a way to get this to work...but the legality of that is questionable and probably can't be discussed here.
Hopefully the fixing the launcher path will be more fruitful.
Best Answer
No, but:
You can try moving your capital to a nomadic county(after conquering it)
Somehow send your heir to nomads, and make him a nomad(so that when he inherits from you, you will be a nomad as well)