Honestly, i think youve made a mistake in your leveling strategy. Yes, missions are ok at best for leveling. you get about a 2.3 xp ratio on most missions. the best ones are the ctp missions at 200 and the starting prejor missions, cause those yield over a 3. But doing missions overall is a pretty bad idea. If you want to read up on the absolute best speed ranker, look at binary man's old posts.
I assume that this is your first run through so i'm not going to scold you on your mistakes, but to put this in perspective, when i do missions i usually get at most half my xp bar filled. when i npc, i easily get 4/5 of my xp bar filled. At rank 450+, its a good idea to start slow, and build your ship up to amazing strength as you go. Work for Drannik as your race, and get as much artifact production as possible. Put all your prisoners into energy, and youll go far.
Now, dont get me wrong. i made some serious mistakes early on too. i honestly didnt know there were planets above extremely abundant till past rank 50 (to show you my luck with the game), and i put 3 levels worth of rank points into cargo. I ended up having substandard artifact production, and only now i am able to catch up to players at my rank. granted, most are ccers with a dyson and some rifts, but thats now the point.
the point is, what may look like a bad desicion at first may actually help you in the long run. read up on the wiki, and you will see that i'm right. Missions are about a 2.3 xp return ratio, and it gets even lower once you finish all the missions and are just left with the repeatable ones. PvP (when youre a lower rank 40-125) gives about a 3.5-4 xp return ratio. NPCing when your a mid level + can give you an 8.0 on some of the easier NPCs. Its all about planning. Plus, when you NPC you can get artifacts to improve the planets you have and your ship permanently. Also, because your rank depends on your ship strength, youre sure not to fall behind and get murdered when you show up on the bt.
And just so you know, when you get to higher ranks, your damage cap increases. since you have no hull or shield, you will most likely die in one shot. and if youre cleared in one shot a halcyon will not help you, as halcs dont protect the ship from raids or hacks. so, not only will you have another disable under your belt marking you as the easy target you are when you fall below a balanced combat rep, but then they are free to raid and hack you. And again, as you level the more resources they can steal from you in one raid/hack. At your rank i'm guessing they can steal about 50 mineral or artifact points, right? when i raid people i get over 1500 mineral or artifact points. Same with hacks. The only advantage you have there is you are rocking scanners so you may be safe from hacks till you hit the higher levels.
Another downside of playing as you intend to, is once youre past 600, not only do alot of nice npcs stop appearing, but players have a very limited battle tab choice. Since you are planning to skip over weapons, hull, and shield, youll look like a cargo multi and get destroyed. Since you dont have any cloak up, this will most likely happen multiple times a day... Trust me. sometimes a player replaces a quantum firewall since theyve been on the bt and i trip it. thats almost a guarenteed disable for me, and i have about 1100 kills, which is not a deterrent at all. Also, since reds are rather hard to come by for higher levels, any way they can get them is worth is for those dominion cannons or base scans.
So, incase you thought to yourself TL;DR, this is the gist of what i'm saying. Talk to Binary Man or read his old speed ranking threads. Its not too late to turn around on your gameplay style, i strongly urge you to mimic binary man's advice and gameplay style (i think he restarted and is already over rank 500? something like that). And yes, we've all made mistakes, but it just takes dedication to work around it. Incase my words fall on deaf ears, i wish you the best of luck, and that you are successful in your gl career.
- research towards energy. 
