Retreat, huge coffer (4100 gold) I always buy these with gold ... it gives you a three day peace treaty (shield) plus a relocation (and some other JUNK) are great ... stay with a peace treaty unless you want a fight.

One month VIP subscription are 8000 gold a month ... you always want your vip going ... (you can get week vip or day vip  from other places sometimes ... ). 

Shaman hero energy 100 (636 gold) is good thing to buy with gold if you don't buy with real cash.

I will look later for other things to buy with gold ...

I waited in writing here, till someone else answered, happy that someone did,especially someone who is smart, as there is nothing worse than asking a question on here and getting a bad response or  worse no response at all.

My opinion is ,the reason you got many different answers previously is because, players have different opinions as to the best way,much as in many other parts of the game. 

There is a difference between enjoyable,best,and efficient ,so its going to be what you think the best use is,at the time you hit spend gold, which is going to be dependant on your game play, where you are in the game, and how much gold you have, and picking up.

I use mine for various things. If I have a lot I use it to upgrade buildings and/or knowledge. To ME thats priority one, two and three. Otherwise I use them for speedups. Those are versatile as they can be used for buildings/knowledge or speeding up troop training. I WOULD NOT use Gold for troops as the speedups are both cheaper to use and will cost way less than if you just paid for the troops.

Gold can be hard to get , depending on your Clan and ability to buy Gold. ONLY get the packages when/if you spend real money. The "extra" Gold is way cheaper that way, buying Gold from the bank is wasteful.

Always try to have plenty of Peace shields and re-locations too.As a newer player, as I take it you are, the Peace shields are probably more needed.

Try to get as many achievements as fast as you can both those you can see and the "hidden ones" as for some of them the Gold is quite substantial. Ask your Clan mates for a list of the hidden ones as the older players SHOULD have them.

I agree that the retreat coffer offering your shield of choice (one day or three day) is the most important as you get the shield and a relocation item at a good (gold) price.  I also agree that thirty day VIP is the best value in the game although, as you progress, VIP activation will look after itself without needing to spend gold.

Resurrections are a poor use of gold although the new 95% discount during Jotunheim might change that a bit.

As you progress, and with gold becoming plentiful from achievements, knowledge and aesir and troop upgrades - even buildings - which require very large amounts of rss and boosts become good purchases.  You can time the purchases to get some collateral benefits like completing quests and reaching checkpoints in an Influence Increasing Event.  You can also add points in CvCs.  Shaman knowledge and Tier I - V troops are good places for this.

Do not adopt any fixed rule about spending.  The single most important thing about gold is its flexibility.  Situations arise in which spending gold may be the only way to resolve matters happily.  So keep a reserve.