Missions & Complexes

solves most problems

Seriously, we can't stress this enough. If you're not effectively applying the DPS, it doesn't matter. Tracking skills and piloting can make a huge difference for this, much more than the fitting in many cases.

My 2 cents.

Each NPC pirate faction has strong resistance to some types of damage, and weaker resistance to other types of damage.

http://wiki.eveuniversity.org/NPC_Damage_Types

Amarr lasers only do two types of damage, EM and Thermal, which means if you are fighting rats that have high resistance to those types of damage, it's going to take longer to pop them, and they get more time to put holes in your ship.

Hybrids used mostly on Gallente ships but also on many Caldari ships have a similar problem, they only to Thermal and Kinetic damage.

If you want flexibility for the type of damage you do, you have three choices.

Missiles, All of the T1 Amarr ships with bonuses for drones can fit missile launchers, some Amarr T2 ships have bonuses for missiles and the Amarr T3 Legion cruiser can also fit missile launchers. You don't need to crosstrain into Caldari or Minmatar to go for missiles, just realise that the T1 Amarr drone ships will rely on drones to make up a very large portion of their total dps. Amarr does not offer any "only missiles" ships in T1, you'll have to train up into Amarr T2 or the T3 cruiser for that.

Drones. Amarr has a decent lineup of ships with drone bonuses, Only Gallente offers a larger selection of drone bonused ships, and it's not a whole lot larger than Amarr offers. Managing drones does require more work compared to doing all your dps from your ship's turrets, but every type of damage available to players is available from drones.

Minmatar projectiles. Just because you are flying Amarr ships does not mean you have to use laser turrets, it is possible to go against the grain and fit turrets from other empires, but you will lose any bonuses a ship has for a specific type of turret. Projectle turrets do not use any power from your capacitor, but they do use a bit more powergrid to fit them. Projectile turrets also offer ammo that covers every damage type and several types of projectile ammo have built in tracking bonuses, something laser crystals and hybrid turret ammo don't offer.

So, the next point. How do you actually test a fit without risking losing an expensive ship? The public test server!

CCP has a test server that is open to all registered players. https://community.eveonline.com/support/test-servers/singularity/
https://community.eveonline.com/support/test-servers/singularity-player-commands/

CCP seeds one station in every constellation with a full range of T1, faction and T2 ships, modules and ammo. A well stocked market is only a few jumps away, no matter where you are. Officer and deadspace modules are not seeded on the market.

Everything costs 100 isk. Want to buy a bunch of different battleships to try out? No problem, 100 isk each. All the modules for them, 100 isk each. Ammo is also 100 isk per round, so that can be expensive, but if you only paid 6000 isk or so for a fully fitted battleship, compared to 200 million+ isk on the live server, spending 250k isk on ammo isn't a big deal. Don't bother insuring ships on the test server, if you lose a ship you get the insurance payout without paying for the insurance in the first place. You also get the bounties for popping rat ships and mission rewards from NPC agents.

Players are not supposed to attack you without your permission on the test server, except for two designated systems, see the test server rules link on the first test server page I linked. This means you can go pretty much anywhere on the test server and not get ganked. If you do get ganked outside the designated PVP systems, you can report the gankers to CCP.

You cannot give yourself skills instantly on the test server, you must train them in the usual manner.

CCP does copy your character data from the live server onto the test server, but only when they need to, it doesn't happen on a regular schedule. A new mirror of character data from the live server to the test server should happen later this month, but an exact date hasn't been announced. All your trained skills, your ships and equipment, your wallet, your standings, etc, gets copied. This can cause ships you are testing to be lost because you don't have those ships on the live server, so save your fits.

use phased plasma. the difference is not that much. BTW gurista are weak to kinetic :
https://eveinfo.com/npcships/612/deadspace-guristas-battleship/