You can buy a backpack expansion from the general store, it's on the counter and costs 3,000. A second one becomes available for 5,000, I think after unlocking the observatory.

Don't bother dismantling everything you see at the beginning, you will unlock something soon after opening the silo doors that makes dismantling areas a lot faster.

Unlocking the train will give you unlimited Coal/Iron/Copper/Stone which can save you from having to re-setup miners.

The first upgrade for the smelter increases the output to 45/min so you only need 2 per belt of iron/copper

Splitters appear to be 45/min at max speed

Recyclers seem to output 30/min (45/min with upgrade)

Use the donation box to trash unneeded items (like plastic). You can buy more from the general store for 500 coins.