You are very weak in the beginning and should run away from most fights. High map speed is very useful.
What I do in the beginning:
First and foremost: Invest the beginning points wisely and immediately train yourself so the combat skills you will need straight away are over 35.
Having a horse from the beginning or very soon will even the odds a bit. Combined with a ranged weapon and a fast melee weapon (to counter my low level slowness and high RL age) I have no big problems taking out five of the lowest bandits but ten high level ridden enemies will usually pawn me.
There are loads of combat tips here https://forums.taleworlds.com/index.php?forums/the-guildhall-general-discussion.140
The arena is your friend in the beginning and so is practise. It is amazing how much difference five thousand hours of gameplay does to your real life skill with the mouse and keyboard.
Do not let their melee weapons hit you and keep moving around so their ranged weapons have a hard time doing so.
Experiment a bit what stype suits you. Personally I rely little on blocking and mainly on dash in, hit and dash out. Many swear by the lance and it is powerful even at low levels if you have a horse faster than the slowest overaged, limping packhorse. I just find it hard to hit with but having picked up a lance on the battlefield early in games I have changed the tide one a few battles.