When I play with gold, First I stack Books of Knowledge. Often I change it to Str, and Resources. But it will cost you since first days you could buy with the price between 2.5k-5k per book. If you have a good amount of gold, you do it like that but you need to be patient, like stack 3 adventure, change stat to str, send robbers and adventure then change it to resources. If you are lucky, or if you have silver as mentioned you should buy Scale armor. But it will be expensive too. Also I need to warn you when you start playing with gold, you will be craving for gold on every server. It is not so balance changer, but when you play this game like hours in a day, It gives great advantages.
About Defensive Gaul weapon, you should buy Phalanx Weapons(spear, pike of phalanx), but some times, you won't be able to send your Phalanxes in time, so go for a cheap druid, or heduan(depends your preference ) weapons. Also it is important to have "Standart"(Small,Normal,Large as game continues) and you can get map for your troops to get back home sooner, it will help you when you have limited time. Phalanx has the most efficiency so I would advise you to get Helmet of Infantry(Mercenary,Warrior,Archon The ones gives Barracks bonus.) but it is okey to have a Helmet of Horseman too. For boots, experience boots is okey but also you can have a shoes of endurance(the one which give speed >20 distance).
Buying those item in earlier days will be hard because everybody will bid it. You can stack you silver from different items, I saw Shield cost 100k silver. Maybe you would be lucky to sell one and use them in new items and some gold advantages.
And as you mentioned that you are a new player. I recommend you to get crop production bonus and plus at some point. Especially in World wonder Era.