For an early-game pick, here's some tips and suggestions:
Slime makes for an excellent rod, a poor head, and an abysmal binding. Quite frankly, it will be the best rod you can make before hitting the Nether.
The head can depend on what you have available:
Obsidian can mine anything in the Overworld. Not too shabby. Steel can as well, if you luck into some in a chest or somesuch. Failing that, Bronze or Iron are not bad for a first 'serious' pick.
For the binding, I really only have two options: paper or Obsidian. Obsidian gives you Reinforced 3, which really lengthens the lifespan of your tool. Paper has the 'writable' property, which gives you an extra upgrade slot. For your first pick, before you hit the nether, I'd suggest Obsidian personally... it isn't going to be the last pick you make, so dumping valuable resources into it is going to be counter-productive.
Once you hit the Nether, go with a Cobalt Head, Mannyllium rod, and Paper binding. This *will* be the best pick you can make with TC.
Cobalt is the fastest mining speed of any material, so unless you plan on mining actual Mannyllium (which I've never had to deal with), Cobalt is the best head. However, Mannyllium DOES have the best durability multiplier, so use it for your rod. With the extra property from the paper binding, you can get Fortune3 from Lapis, Auto-Smelting, Speed, and either Electric or Mossy to keep it going. Lemme tell you, the combination of Fortune3 and Auto-Smelting is just... really a lot of fun.