All of these go in the raw/objects/entity_default.txt file. There's a lot you can do here that can effect what you can bring, but I'll just focus on the tags that give you free crap.
Also, it's possible that EVERY race gets a free anvil, but I'm not sure.
[DIGGER:ITEM_WEAPON_PICK] allows your race to start with 2 free picks of the lowest value metal, generally copper.
[WEAPON:ITEM_WEAPON_AXE_BATTLE] allows your race to start with 2 battleaxes of the highest value metal available (actually, the metal depends on several tags), generally steel; you need this or another usable weapon if you want to be able to kill trees. Other WEAPON and ARMOR tags are useful, as they allow you to purchase additional equipment at embark, and later allow you to forge them, but you don't get them for free.
[METAL_PREF] will cause your weapons and armor (including your free battleaxes) available on embark to be made of the highest metal available, and thus giving you more points, should you decide to sell an axe. If you do not have this tag, you'll get iron battleaxes (and other weapons and such available on embark will be cheaper to buy). It may have an effect on individual dwarves' preferences.
[MINOR_METAL] will cause your available weapons and such on embark to be made of copper, so axes will give you less points should you sell them, but other equipment will be cheaper to buy.
[USE_ANIMAL_PRODUCTS] and [INDOOR_FARMING] may affect the free food you get. If you have [OUTDOOR_FARMING], you may still get free food, but I haven't tested that.
Hope these help.