Iguana Tweaks and some custom Tinkers' Construct configs make your entry into this pack much different than you might be used to. Punch a few trees first still, but then everything changes.
Vanilla wooden and stone pickaxes (and some other tools) are still craftable to allow certain recipes, but they have been made useless as tools. You will need to craft a Tinkers' Construct pickaxe, but wooden pickaxe heads are uncraftable. Flint is your starting material of choice. It is not found randomly by mining gravel anymore, but rather by crafting four gravel in a grid, or by two gravel in a diagonal, like flint and steel.
Wooden and stone swords are uncraftable in both Vanilla and Tinkers' Construct recipes. To defend yourself, it is recommended to craft a Flint Mattock using Tinkers' Construct and a bow if you can manage the string. Dungeon Crawler Knives, while intended as more tool than weapon, will also work in a pinch. Additionally, you may craft simple armor using wooden logs.
Food and ShelterEdit
Once you have a usable pickaxe and hatchet, gathering materials for a basic shelter should be no problem. Food gathering is mostly unchanged, but there are a few new options that may help early on.
Barley can be found growing in the wild. This can be harvested and used to make bread just like wheat. While unusable as a replacement for wheat in crafting, barley does grow much faster. Additionally, barley (and wheat) can be crafted to get flour at a 1:1 ratio, which can be cooked in a furnace for more efficient bread production.
Berry bushes can be found scattered on the surface. Berries are not very filling, but they make a nice, easy snack. Bushes can be harvested and replanted. There are also strawberries that you can harvest in large patches, and you can craft them to obtain seeds.
If you find an apple, it can be crafted into an Apple Core, which can then be planted as an Apple Sapling. Once grown, this tree will produce apples on its lowest layer of leaves.
Rotten Flesh, which used to be nearly useless can now be crafted with a Dungeon Crawler Knife to cut off the gross stuff and make raw pork. Alternatively, it can be cooked in a furnace to make leather, though that's not really food.
All raw vanilla meats (Pork, Beef, Chicken, Fish, Rotten Flesh) can be placed on a Drying Rack from Tinkers' Construct. If left hanging for a few minutes, they will turn into tasty jerky versions, which are about as fulfilling as their cooked counterparts.
In terms of shelter, not much has changed. The old options of digging yourself a hole and covering it in dirt, or building a wood/dirt shack are still viable. However, you want to make sure that there are no gaps in the roof or walls, as mods like Lycanite's Mobs and Grimoire of Gaia add mobs that can fit/shoot through one block spaces and mobs that can fly/jump/climb over walls.
There are also several cheap defensive blocks added by Tinkers' Construct, Dungeon Crawler, and Torch Levers. These include Punji Sticks (essentially spikes), Barricades (Blast Proof and take forever to break for PvP defense), various Spikes (Spider Eyes and Slimeballs can be added to make them poisonous/sticky), and Collapsing Slabs (fall when stepped on).
Any basic starter home will want the following: Crafting Table/Crafting Station, multiple Furnaces, Pattern Table, Part Builder, Tool Station, and a Bed to set your home.