The balance in vanilla is actually quite good for shorter games. Clamming has pretty high opportunity cost. It takes something like 15 turns to get even for one clam. 30 turns to give u 100% profit. And you need a way to turn those gems into power. That usually means wish which also has opportunity cost. In long game it will brake the game. In short games u will probably want kitted bane lord or two instead.
The problem with hammer is that usally the gems saved with hammer are used with hammer. In a way u get double bonus. 30 gems = 6 frost brands. 30 gems + hammer = 10 brands. Thats 2/3 more brands. From 25% forge bonus
One of the options for balanced nations is to go for those high power nations. Like Pythium, Acro, Tien chi, Marignon, Jotunheim, Ermor... Ermor has quite difrent way of playing then others thou. If ermor is not wanted then the last one is harder question. Bandar and Pangaea both have good sacreds. Eriu and Vanheim both play pretty difrent than others. Ulm and agartha are both way too weak. Maybe machaka or man would be best? In my opinion they both are weaker than others in the list.
Playing vanilla dosen't mean no house rules. If u want no clamming in bigger game that can be the solution. I haver played some games where all players are allowed only 5 gem gens. It makes u think do you want to have clams or blood stones. House rules usually work well when u just make sure everyone knows what are being used. And make sure no player is called norfleet