Basically, newbies to the BD will want to use weapons that do at least 6 icons. Don't bother with anything less. When you start getting into it a bit more you can go for 8-iconers and 10-iconers. The next step is 11-iconers/13-iconers, and then you get into the big expensive stuff like the 16+ icon Sword of Skardsen. I'll give a few examples at the end of this post.
Many people seem to go for a set structured like this:
1. Main attacker (strongest)
2. Secondary attacker (equally strong or a bit weaker)
3. Dual-duty (attack/defence) or a third attacker
4. Healer
5. Bomb (once per battle)
6. Pure Defence
7. Freezer
8. Stealer/Reflector/One-use Bomb/etc. (rotates depending on enemy)
I posted this for someone in another thread, but it can apply to those of you who are just starting out, or have a little BD experience but not much NP. It's a good beginner set, and all pieces are an excellent value.
1. Obsidian dagger (6-8 icons) (550 NP)
2. Bone Sceptre (6 icons) (300 NP)
3. Scarab Ring (6 icons each of attack and defense) (1.5K)
4. Greater Healing Scroll (heals 50 HP) (30K)
5. Illusens Earth Potion (6-9 icons, once per battle) (2K)
6. Downsize! (blocks 50% of an attack; a MUST) (8.5K)
7. Snowglobe Staff (19% chance of freezing) (25K)
8. A one-use item/stealer/shield (sticky snowball, fire muffin, leaf shield, patched magic hat, purple sticky hand for challengers that have good stealable items... basically, rotate in whatever works best)
Once you get to the point where you don't mind spending a little more, you can stick some of these things in there (the BFC is 400K; the 9/10 iconers run about 550-850k; the 11-iconers are about 1.5-2 mil; the 13-iconers are about 3.5-3.7 mil; the H4K and F-pot are about 5.5-7 mil):
Black Frost Cannon (better chance of freeze)
Pike Pike (9 icons)
Scuzzys Comb (10 icons)
Ramtors Spellbook (10 icons)
Goo Blaster (11 icons)
Garoo Elite Blaster (11 icons)
Fungus Ray (11 icons)
Bzzt Blaster (11 icons)
Wand of Reality (13 icons)
Bow of Destiny (13 icons)
Honey Potion (14+ icon bomb)
H4000 Helmet (100% freeze)
Freezing Potion (100% freeze, 2 icons)
And after that comes Hidden Tower weapons like SoS, Pirate Captains Cutlass, Ghostkerbomb, Mask of Coltzan, etc.
And IF you have trained defence to match your strength, these dual-duties (attack and defend at the same time) are good. I'm not a defensive battler myself and I can't recall the exact stats.
The IDB is down, so I can't check, but when it does come back you can do a search.
Tooth of Terask
Amulet of Inevitable Betrayal
Cloudy Wand of Storms
Frozen Wand of Crystals
Sword of the Dead
Dusty Magic Broom
Also, the useful faerie abilities:
Drain Life (drains 10% of opponent's HP and gives them to you)
Burrow (blocks a whole bunch of an attack; can't remember exact percentage)
Sink (like burrow, but with different icon types)
Regeneration/Restore/Water Vapour (heal 33% of lost(?) HP)
Fiery Gaze (chance of freeze)
Diamond Dust (slightly better chance of freeze)
Then there's Quench, Steam Shield, and all the other full blockers, but I can't remember them off the top of my head, so see IDB's section on faerie abilities when it's back up -- it tells you which ones are useful.
Obviously, don't take all this as BD law -- my set examples tend to lean more towards the offensive rather than the defensive, and someone with matching strength and defense boosts will probably set theirs up differently. Also, I'm primarily a 1-player battler -- if you want to use the 2-player BD, it's a whole different animal and you'll be probably be doing a lot more defending and reflecting than flat-out attacking. But the weapons I've listed are some of the most commonly-used and the best value, and should work well for any new or intermediate BDer.