So many questions... welcome to DF!
First, letting a young fortress just run is risky, esp if you're doing digging around water/etc. Doubly so if you're new to the game. This is not "Sim City" where you can just let it cook along - well, not at first, at least. Takes some management, esp to respond to the unforeseen.
Now, speaking about foresight, it's good to get the basics down EARLY. Hospital, Well, food production chain, defenses - partial checklist here:
http://dwarffortresswiki.org/index.php/40d:What_should_I_build_first(Not going to ask why you're in a hurry for the caverns - diff discussion. Have fun!)
Caravan needs a 3-wide path. Ramps only on straights - no ramps "in" the corners. Guard animals on chains ( {b} {v} ) do not block caravans, but "traps" do. (But you could build a U-turn 4-wide, and trap the inside of that corner - that works well!)
But remember - Caravan only stays a certain amount of time, and if "kept" on the map too long bad things can happen (like not returning - if you care). So you don't want a death-march to/from the Trade Depot. Also, your dwarves need to carry trade goods to the TD - so it should be central to whatever industry(ies) you are going to use to trade for stuff.
If you want to maximize embark, start with (or without) 1 pick and DIY the other 4 picks (and maybe some bronze weapons for early defense - axes, hammers, cross-bows?), and spend the rest on more food/drink.
The wiki is absolutely minimalist - adding more ores/stones helps a lot for very little extra cost:
http://dwarffortresswiki.org/index.php/DF2014:Make_your_own_weapons#Better_bronze_supplies(But if you bring just 3 of each booze-seed and put 1 dwarf on growing/brewing asap, you only need maybe 6 of each booze to start - only 1 Dwarven Wine if you bring 5 Plump Helmets and brew those immediately for even more of those seeds to plant.)
OTOH, if you really don't want to medium-manage anything, buying the picks, 16 booze each and buying a mountain of food will do the job just fine.