Minecraft Wiki has a table of damage done by weapons.
Swords: The best ordinary weapon (by damage numbers) you can readily make is an iron sword, and the second-best is a stone sword, which is very easy to craft since it only requires wood and cobblestone.
Bow and arrows: I strongly recommend keeping a bow and arrows, if you can, because it enables you to kill monsters at a far distance (especially important since spiders jump at you and creepers will explode without actually touching you). A bow requires three string and three sticks, so the hard part is killing enough spiders to get the string. You could:
- Kill spiders in the morning, when they will only attack you after you attack them and so won't swarm.
- Build a trap for wandering spiders; for example, a wall of cactus which you're on the other side of. However, this isn't as easy now that spiders can climb; you'll have to put an overhang on top so that they climb up it and stop.
- Or just kill spiders with your stone or iron sword.
Arrows for a bow are made from flint, feathers, and sticks, or are dropped by skeletons. Flint is readily obtained by mining gravel (any gravel that doesn't produce flint can be re-placed and mined again for another chance at flint), and feathers may be obtained easily from chickens.
Burning: It is possible to set enemies on fire, but it doesn't kill them very fast. A more practical possibility is to drop a bucket of lava. The safety of this depends strongly on the terrain (you can outrun lava unless you're clumsy, but the real hazard is if the flow blocks you from walking back to pick up the source), but if you can do it then it will bog down the enemies that try to chase you across the lava and kill them reasonably quickly.
Armor: Also, find a herd of cows and start breeding and slaughtering them to make leather armor (24 leather makes a full set). Armor makes you take a lot less damage, if nothing else so you can get in some aiming and timing practice in those beginning fights. Also, killing cows and chickens will help you learn how far your weapons reach and how to aim at a mob.
On the Keeping of Cows and Chickens: Passive (non-hostile) animals spawn rarely, mostly on initial world creation. Therefore, in order to obtain the leather and feathers I recommend above, you will need to breed them. A complete discussion on breeding would be a bit much, so I'll just point you at Minecraft Wiki on the subject. The short version is that you should construct a wheat farm (as wheat is required to initiate breeding) and a pen for the animals. If you do not breed animals but only kill them where you find them, you will be waiting a long time for the population to recover. Also, baby animals do not drop any items, so you must wait for them to mature.
According to the Wiki Itself
A bow will likely be the best weapon for dealing with a witch, as the splash
potions have only a short range (at most nine blocks) compared to arrows (which,
when fired straight at full charge, travel 24 blocks). If a bow is not an option,
a direct melee charge is the best option. Due to the witch's slow attack speed, if
the player runs in a straight line and manages to get a quick sword strike in,
the witch will try to heal themselves with a potion of healing, leaving the player
to attack them without fear of retaliation.
So by the sound of it, if you haven't yet got a bow to fight (which early on you probably don't) the best option is to dodge their first attack, then charge in swinging your sword. With a charge, your first strike will probably be a crit that will force the witch to heal, and then you can barrage them with sword blows until they're taken down.
This might be counter-intuitive with other mobs around, since rushing in is the last thing you'll want to do against them. It would probably be a good idea to take out any wandering mobs first before dealing with the Witch, if they're all gathered together. If they're not, then it'd be best to charge the witch and take her out very quickly, before running away from the rest to attack at leisure.
Best Answer
If you have MFR, a single biofuel bucket in a furnace generator generates 281250 RF at 40RF/t. With MFR BioReactor you are able to at a bare minimum generate 80mb per item, which equates to 22500 RF/t, which is already more than baked potatoes in your culinary generator. Because you already have a tree farm, you can pump the extra saplings in and get more energy off of your existing setup. You may consider adding more tree types into your tree farm to get more energy per item.
If you want the most efficiency (and have the patience to wait for it to generate the energy at 5 RF/t), run the biofuel bucket in survivalist generators
If you are not stuck with Extra Utilities, the BioFuel Generator from MFR gives a whopping 800,000 RF at 160 RF/t