RELATED UNI-WIKI REFERENCES
Gallente Battleship bonuses (per skill level):
The Megathron is is a gun boat, specialising in large hybrid turrets. With its 4 mid slots and 8 lows the megathron is almost exclusively armor tanked. The Megathron is somewhat of a spiritual successor to the Brutix and Thorax, favoring guns over drones. However, the Mega can fit a very thick tank and has the bandwidth and drone bay to field either a flight of 3 heavy drones or full flights of both light and medium drones to back up its destructive force, making it a powerful option for many different kinds of PvP and PvE action.
Gallente Battleship III/IV: Get this before taking it into PVE, and at least IV before going into PVP.
Large Hybrid Turret IV/V: The primary training for a heavy Gallente DD. T2 Blaster Guns allow you to fire Null ammo, which will greatly increase damage projection whilst still keeping your dps high.
Sharpshooter IV/V and Motion Prediction IV/V: The two most important gunnery support skills, increasing optimal range and tracking speed. Both need to be maxed for T2 Rails and Blasters respectively.
Surgical Strike IV: Increasing DPS across the spectrum of all turreted weapons, whats not to like about this?
For more info on fittings, please go here
Bringing the Megathron or any Battleship into PVP is something that has to be worked towards with both a large amount of Skill Points and actual long term game experience to bring the most out of the hull. Once you land into the battlespace, you must be sure of how you're going to move, (unless you have Basi Logi with cap transfer help or an ancilliary cap recharger), whether it be to anchor or move into range of the primary. Given how slow a BS moves and how long a typical engagement lasts, you will either be a useful contributor to the death of the primaries, or have been completely useless having been out of range for most of the time, or currently sitting in your POD lamenting the relatively expensive lossmail.
Listen very carefully to the FC during travel or combat, a warp to the wrong gate/destination, due to a misheard command means lots of time wasted due to the slow warp speed of the Battleship. In hostile territory, doing this can be a death sentence.
If you're MWD equipped, right click on the module, and turn auto-repeat off. This will force you to pay attention and manage your MWD to use it, potentially saving you vital cap energy. Do the same for any ancilliary rep/boost module. Actively and effectively managing the internal resources of your ship during combat is a skill that will also mean the difference between losing your ship and taking it through a battle successfully.
In addition, the battleship is also the ship where, more so than any other ship you will fly in EVE, your battles are won and lost at the fitting screen before you even undock. Never undock the battleship without a plan and without knowing WHO you're going to fight/hunt. Fit and equip accordingly, preferably in a fleet with a specific doctrine.