At warlord, the "trading techs" idea won't work too well. The AI builds very slowly at both chieftan and warlord, roughly even with you on regent and monarch, and faster then you on emperor and deity.
You don't want to turn tech to 0, and rely on the AIs to get techs for you to buy. Your game will take too long that way. You'll have lots of money, but nothing to spend it on...
What you sound like you're having a problem with is the diplomacy part of the game. What I would do is take advantage of the fact you have all these techs (and can get them before the AIs).
Crank your tech up. Expand as quickly as possible. Then *sell* those techs to your nearby neighbors (don't worry if they don't have much to give you, take whatever they have). *Give* those same techs to the civs farther away (like perhaps on the other side of those nearby civs. The idea is to make really nice with the guys farther away then nearer (you *can* be nice to someone nearer then you if you feel they are a threat though, and this will depend on how many "near" neighbors you have).
You should trivially be able to out expand and out produce any single AI civ at Warlord. The trick is that you probably can't out build all of them combined.
When you get writing establish embassies. Buy and sell as much as possible. Wheel and deal. Check possible trades as often as possible. Always be willing to give stuff to the AIs. Pick a nearby enemy. Make *really* good friends with the folks around him. Then, either start a war with him and then pay your "good friends" to join you in a military alliance, or (later) get MPPs with those good friends, declare war on the nearby civ you want to conquer, get him to attack you first (this is key), then when he's busy fighting off about 4 other civs, you can easily pick off all his cities that you want. Um... by "declare war", you can use more subtle tactics like demanding tribute over and over, sticking units in his land to get him really pissed at you, and anything else to get him "furious" at you. You don't have to just hit the "declare war" button.
Set a goal for your game. If you want to win by conquest, plan on working the AI's the way I said above. Get them to fight among eachother, then pick off the pieces left. You *should* be stronger then any single civ at chieftan/warlord level. Take advantage of that. The AI will always pick the "weakest" target to attack if possible. However, the AI's as a group will gang up on the strongest target if they are given a chance. The strategy should be clear. Make sure you aren't the one getting ganged up on. If you haven't spent any effort making friends, then when you invade some random AI, they will alll gang up on you, and you will get squished, no matter how much stronger you are. If you make friends, then you can set up the number 2 guy as the "bad guy" that everyone will gang up on. It just takes a bit of planning ahead...
EDIT: Let me clarify something about "the AI will always attack the weakest civ". I wasn't really clear.
If no one is at war, and you are the top dog. And you haven't made any effort to make people happy with you, then when you go to war, many of the civs will join forces against you. This is the "bump off the strong guy" aspect of the AI's programming.
However, during a war, the AI picks specific targets based on his odds of winning the battle (there's more to it then that, but that's close enough for now). The AI also does not particularly distiguish between *which* civ he's attacking once he's at war. He just sees units and positions as "enemy" targets and chooses among them based on his odds of success (and proximity though!). Thus. If you are the *only* target of the AI, he'll send everything at you. However, if you and 4 other civs are all at war with a single civ at the same time, and your "allies" are weaker then you (in unit type and/or number), guess where he's going to attack most? Prudent use of that tactic will allow you to both remove a powerful opponent *and* weaken severarl other AIs at the same time.
If you want to try diplomacy, then work on that instead. Get others to fight, and stay out of it. Build up culture instead. I played a game recently (as the Germans no less! Just wanted a silly challenge I suppose), where I did not start a single war. I actively worked to avoid wars, and engaged in them as little as possible when they occured (always working MPP and alliances to get others to fight around/through me). I never got a single GL. I never built a single army. I captured about 15 AI cities with culture alone. I absolutely squashed everyone without firing a shot. I won a UN victory by unanimous vote (except for the moron second place guy who declared war on me one turn before I built the UN... sucker!).
Once you've got the basics of expanding and building down, you need to master working the AI's. There are a ton of articles on this site about how to do that (and I'm not going to repeat them all). The key though is to always keep a long term goal in mind, and to always make the AI's do as much work for you as possible. Oh... And work to keep the AI's happy with you whenever possible. While it seems counterproductive, you will gain more in the long run by giving stuff away to AI civs, then by hoarding it for yourself. Being "the nice guy" (at least to the civs you want to work for you) is the key to really putting the screws to the AI civs...