I'm wondering whether I should get an Antigua or Sealed Sword first. I don't exactly specialize in any one weapon, so the gun vs sword argument is out.
What should I use my Jelly Gems on?
With the recent buffs to the antigua line the guns are now very useful, they always have been the easiest guns to use in the game with a large magazine, rate of fire and bullet speed. If you choose to get one of these guns first then the argent peacemaker line is generally the best one to start with as constructs and undead tend to give newer players more trouble than slimes and ranging them is more benificial.
Personally I've always found Sentenza to be not as useful as the other 3. I used to have one but sold it shortly after unbinding released. (now regretting but i dodn't know the buff was coming :P ). It'd still be the last one on my list though.
As for the heavy swords, it is a completely different play style to the 3-swings you'll be used to. Might be a good idea to buy a Troika off the AH (they're very cheap) just to try out them out first, run a T" run with it and see if you likes. If this is the case then Go for the swords first.
Out of the swords I think that Faust is probably the more useful (though less used) as a starter in heavy swords as you'll quickly find that with a bit of timing jellies and gremlins are VERY easy to kill with it :)
Hope this helps :)
Faust is harder to use since it can self-curse, so you need curse resistant armor or extra weapon slots. You could go with whatever you do not have from elemental sword, shadow sword, elemental gun, or shadow gun.
Also, a sealed sword>avenger or antigua>silversix would help with Roarmulus twins, and with FSC later. Even just a sealed sword will be useful a lot of places since it is normal damage.
Then it becomes preference. Do you like ap, sent, da, or faust?