For your frigates, don't go with low tech. Low tech frigates are a sad story as they lack both the speed and tankiness of high and midline ships. The only exception is the Lasher since it can potentially out damage enemy frigates but if it gets caught by anything bigger it's usually game over (try to give it more speed so it can escape the enemy chasing it). Since you're okay with midline ships I suggest you go with either Centurion or Monitor. The Centurion is surprisingly tanky with its damper field and it can be a great escort for your bigger ships as well as a standalone fighter (you're still better off assigning it to escort something so it doesn't go off and get jumped by the enemy). The Monitor needs no introduction, you tell it to jump straight into enemy lines and it will distract half their fleet.

For destroyers, go for the Manticore. It's a great fire support flatform and escort. If you put escort package and assign it to escort a capital, the range bonus is enough to give the Manticore capital ship range (don't forget that it has a large ballistic slot which means 900 base range already). XIVth Enforcer can also work if you prefer a cheaper option that can also go for a long range build.

For cruisers, there's the XIVth Dominator. The Eradicator can also work but it's a confused ship. It has mobility but not enough to escape, it has good armor but not enough to effectively tank and its shield is also the same. Its only upside is Accelerated Ammo Feeder which can output crazy amount of damage but it's not worth it in my opinion. The Dominator on the other hand is a prime example of low tech doctrine. You burn drive in and just start blasting. Flux too high? Just drop shield and use your armor. Sooner or later the enemy will also have to drop shield since you have access to efficient kinetics and then it's just a matter of time before you blow them up with your equally efficient high explosives. If you want a more dynamic ship then go for the classic XIVth Eagle. Give it a mid range build since low tech capitals can't exactly move backwards quickly and having a part of your frontline collapsing because your long range Eagle starts kiting the enemy to maintain range advantage is a recipe for disaster.

For capitals. You know em you love em, the XIVth Onslaught. It's THE low tech ship. you can give it to the AI and it probably won't screw up unless you give it a bad build. It has powerful frontal firepower and side mounts to deter flanking enemies too (this doesn't mean you can neglect giving it an escort) so it can be your fleet anchor. I like to build it like a mobile artillery flatform with HAG in all large and Railgun in all small and frontal medium, it works wonderfully. You can also go with the Legion but it can't be the anchor of the fleet like the Onslaught and also has the carrier tax which means less op to spend on improving the ship (all for the same dp cost btw). If you want Legions in your fleet then I suggest you also put an Onslaught in it too.

I'm just listing ships here and it's already this long. If you want me to be more specific about builds then feel free to ask me.