I am at level 61 right now. I also have a feeder city (which has grown to level 32 now). My storage is now 465, so note that I had a lot lower capacity at lower levels. I have kept storage to 125 on feeder.
What I write is based on my experience with both cities:
1. Focus on storage + one other expansion (beach/mountain/land). My suggestion is to get done with mountain/beach first after expanding land to some extent. I suggest expanding storage at all times since you keep needing it for everything anyway - war, vu, and what not.
2. If you are in a club, make an alliance with someone for helping each other in expansion. This way, you don't pass off items to global, but help someone to expand and they help you.
3. In our club, we also do even trades for such items (beyond alliances)
4. Currently I need 20 of each type to expand storage to the next level (i.e. 470).
5. Even now, I have a policy of hoarding not more than 5 items of a type (unless the items are going to be used for a purpose). After every CoM, I sell off the items except those used for my routine coin making (more about this later). I don't hoard any basic items (feed, mineral, etc.) unless needed for an assignment / routine coin making.
6. Nowadays I have more scope to hoard vu. But I have never hoarded more than 10 per type in the past. During CoM you may add more just so that you have enough for Vu assignments.
7. I never hoard more than 5 of a type for airport items
8. I used to limit 10 of a type for war, but then slowly took it up to 20, etc. Just figure out a balance of how much of the storage you want to spare for war.
9. I have maxed my trade depot (32 crates) and all my stores (thats 11 slots each). I added slots to stores in order of commonly used stuff (fast food got maxed out last since it was least used)
10. Routine coin making: This has to be changed with region upgrade, but this is what I have done so far:
- factories reserved for textile
- make flour, donuts (buy sugar, unless you make it at night)
- make hammers, nails and then chairs
- when chairs assembly is full, make shovels and glue
- use shovels to make grass or saps
- glue and textiles for shoes
- at night, I stock up factories for chips and glass and make TVs in the morning. This takes care of this store for the day.
11. The above helps build up my sim coins. I have then used global market/club members to buy for my epic assignments (I hoard upto 5 of each item during Com to help epic, vu repairs, etc.)
Hope this helps. I am still figuring out the setup for regions, but I am going slow on the same purely because I first want to collect coins for the deluxe market (green valley) and then the rest.