"making a profit" and "cheapest ever" are not the same. If you're dropping 17k on ASCR, then you won't be using the cheapest mods ever, at some point you're going to want to put in a little more to get the most out of your 17k investment. If you're half decent anything under 30k will consistently make a profit assuming you're half decent, although it won't necessarily make the most profit. But if you're going to be using a 17k weapon, there's not much you can do about that. Keeping it under 30k is a manageable goal and won't gimp you. Lets talk some basic rules.

-don't compromise too much on survivability
-you probably don't want to give up your sidearm
-don't leave empty slots to save isk (ie using militia mods and running out of fittings)
-damage mods and uplinks are fittings intensive, probably don't use them.
-more fittings skills = cheaper suit, many mods have identiical performance between militia and basic, where the militia
costs less but use less fittings

first is suit choice. The choice is between militia caldari medium (free w/ caldari race), and Assault C-1. if you're skilled at 3 or higher in caldari assault, the C-1 becomes a better choice. The absolute best choice are the BPOs for caldari assault. There are a bunch of these as caldari is the preferred race for the assault BPOs (raven, dren, dragonfly). The militia doesn't lose you too much, basically you lose the bonuses, 4 pg, and one low slot (not the end of the world).

Ideal suit for me w/ your skillset would be something like

Assault C-1 BPO
Adv Assault Scrambler rifle
Toxin SMG BPO (or basic flaylock since you're skilled in that, no bpo i think however)
Basic or enhanced shield extenders
Basic or enhanced shield regulator
Another regulator OR 1 basic armor repairer OR ferroscale/reactive/whatever plate, however you like to run it (i don't run caldari)
Basic locus/av nades
Compact nanohiv (extra cost made up for by reduced CPU, plus reps you if you have no repper)

Then, once you're happy with the fit, go back and replace basic mods with militia until you've maxed out the fittings.

If you want to go even cheaper and don't have a BPO, use a militia suit (free if you're caldari). This has one less lowslot but the same CPU, so you can convert more gear to militia (basic extenders, basic regulators, basic repper are prime candidates and maybe sidearm or grenades).