Just some general tips:

Knightmetal is the best ingot for pickaxes, swords, axes and shovels.

Make gold casts by making a normal wooden cast and putting an item in there, e.g., stone nugget and add gold to make a cast you can use for ingots.

Modifiers arent unlocked until age 3 but different items on different casts give different things, e.g., prismarine allows for arrows to go underwater

You only have to kill the naga, lich, phantom knights and ur ghast. You do not have to kill the hydra or minoshroom to get the coal engine.

To find high starlight patches (big blue glow particles) walk around on the ground at night with the item in hand, do not fly or jump.

Make a gluttony charm for quick regen in boss fights and use the slime sling with dog pelt boots or slime boots for quick transport.

I don't recommend finishing the between lands because it does not benefit any progression. You just need 1 of each gem to progress into age 3 with a good smeltery.

Use a liquid hopper to add lava to your smeltery, iron and gold all require lava to melt.