The reason you focus on 1-2 weapons is because some resources are hard to come by, so you can usually only upgrade one or two weapon trees until much later in the game, unless all you do is farm but that is a good way to burn yourself out.
Melee is definitely easier to start with especially if you want to pick it up and go asap. I think Katana, Lance, Hammer, or Dual Swords are all great beginner weapons with different strengths and weaknesses.
Katana - High damage, decent maneuverability, can cut tails off easily
Lance - Great defense, medium damage, okay maneuverability, sharp weapons for more damage and good chances to cut off tails
Hammer - High damage, can KO monsters for more easy damage, okay maneuverability
Dual swords - High damage, amazing maneuverability, dodging is your defense, can cut off limbs but blades are shorter so its harder
I did Hammer in Tri and I loved KOing monsters. I did DS in MH3U and I feel its the highest dps weapon in the game if done properly.
There is a lot of little stuff to learn here and there. Make use of all your resources, kill each boss a few times, don't farm EVERY armor or weapon, make some goals on what you want to make, don't get discouraged if you have trouble, etc. There are a ton of helpful posts in this thread, but if you have any specific questions I'm sure anyone here is willing to help a fellow hunter out.
