There was a time when I didn't touch slotting until level 22. I still tend to do that when I'm uncertain how much I like a build. Now that I have a built up supply of currency and attuned IOs, I can slot starting at level 7 in some cases. I might slot some lesser IOs(common, uncommon) until I hit 27 so I can slot level 30 IOs from certain sets as those are more likely to end up in my final build. If I was starting over, building up a stash of attuned IOs would be goal #1.
An anyone can do starter kit to get a few million going.
1. Do the tutorial in the game.
2. Keep the inspirs.
3. Once you leave the tutorial, use /ah in chat to open the auction house. Sell the inspirs.
5. Find common salvage in the auction house and put as many stacks of bids as you can for say 100 currency.
6. Sell the ones you get to the vendor for 250. Rinse, repeat.
7. Eventually move to level 50 common IO recipes and sell those. What happens after that is up to you. I need less than a mill to mimic what I do now.
8. Add in doing content arcs and TFs to gain merits. Outside of the merits, TFs drop better recipes as a reward.
9. Grab the Inner Inspiration power from the P2W. Every 20 minutes you get three free inspirs. Sell or use the better ones.
10. If you are really that hard up for currency, skip the 2x booster. Leveling twice as fast with getting even less funds isn't what you are looking for. Hell, I know how to use the market, and I don't grab the 2x booster as I find the leveling process more enjoyable. I find builds which I got to 50 using 2x boosters need more time for me to feel them out.
Bonus. Keep playing your level 50s. No character has better access to gaining currency than a level 50. A single night of gaming can get you more than what you gained in repeating steps 1-7.