Questions about a game in progress

[lillumultipass]

Hi to all!

I have started playing Dom 3 a few days ago (after playing a bit of Dom2 way back in 2004, but not much since my PhD took most of my time! But now it is almost over!) and I am looking for some advice since I can be considered as a noob (I have to add that my usual playing style in strategy games a la Alpha centaury for instance, is to turtle and be the best in research. This is usually what I try to emulate in Dom3, but I am not sure this is an optimal strategy).
Indeed, my first three games ended in disaster after a few turns while I was experimenting with some new nations and imprisoned pretenders on the Aran map; Then I decided to go back to the basics in order to address two of my main problems, namely, province defense and magic site searching. To this end, I build on Ulm middle age, with a rainbow master alchemist (my mistake was to take Nature 4 and only F1), Order 2, Productivity 2, Drain 3, Misfortune 1, and a dominion of 5. The idea was that; since Ulm units cost a lot of resources but are very resilient, a few would be necessary to expand and gold would not be an issue with Order2 so that later on I could buy a lot of province defense. Also, the rainbow alchemist was supposed to be my site searcher early on.
So, I started a game in the Aran map against 5 Normal Random AI, with Indy strength set at 5 and magic sites at 50.

Everything went according to plan initially and I was able both to expand and to find magic sites while keeping a lot of gold in my treasury. Soon, I was able to build a second castle and I found my neighbor, Pangea then my second neighbor, Agartha. Now, I am in winter of my third year, I have just beaten Pangea and I am on the verge of building my fifth castle. My treasury is 9137, with an income of 3019 and an upkeep of 863. I think I am at a turning point since I am going to clash with Agartha which is the second most powerful nation (as many provinces and forts as me, larger army, but they are way behind in research.). Although my armies were sufficient to now, am I afraid that my lack of magic might be detrimental in the long run so I wonder what I should do. I have started to build a few items to boost my pretender (like ring of sorcery, crystal coin, earth boots...) such that he is now F3 A2 W3 E3 S6 D3 N5. When I have a sufficient amount of astral gems, I will build a ring of wizardry. Then, what should I do? The problem with Ulm is that my master smiths are only F1 E2 so that my magic is very limited. I have discovered a province where I can buy Jade Sorceress which will help me in getting Nature magic. But what else? As to my gem income, I am not sure it is large enough: F+6, A+2, W+1,E+8,S+1,D+3, N+7.
I have a mage cast Gnome Lore every turn, and my only mage with F2 casts Augury. Is it enough? Basically, I can't use my pretender any more since he is forging items. But I don't have access a lot of astral pearls, but I can't forge Clam Pearls since I don't have a lot of water gems either.

By the way, how do you usually search for magic sites? Here, although I had a pretender dedicated to this, I don't feel like my gem income is sufficient...So, I wonder how people search without a rainbow mage. Do you dedicate a large part of your mages to remote searching?

As to the game at hand, any ideas are welcomed. I don't have a lot of experience with high level magic or items, so I am a bit at loss of what I should do next. Thanks for your help!
I know this kind of question depends on the specifics of the situation, but any suggestion would still help me.