You will do better putting your money into pass rush then just into the secondary. The Giants won a SB basically because of their pass rush in 2007. Meanwhile I have not seen a top secondary with poor front 7 win a SB. Have you?
However the reality is that you need some kind of balance between front 7 and the Secondary if you want consistent results.
In the end though you can build good O lines and D lines cheaper than filling up skill positions or secondary positions. And they last longer on average. So if you are building a team from scratch you START on the lines.
The 2007 Giants had zero 1st round picks along the DL (kiwanuka was playing LB) and it's 2007 rookie 1st rounder started at CB.
The Giants spend HEAVY resources on DL and coverage guys.
I value DL quite highly myself but we absolutely blasted the Giants to open last season by picking on bad coverage guys. It was just too easy.
It absolutely requires a mix because even the best pass rushers can be minimized if the coverage unit doesn't do it's job for a few seconds every play.
As to what it takes to build lines I disagree. It is not easy to fill those spots. Dallas has been VERY lucky with DT but it used R1 picks on Ware and Spencer.
Hatcher was a R3 pick that needed years to develop to where he is now.
We've also got Crawford in as a high pick recently.
On the OL we've used R1 picks for Smith and Frederick. We've sunk big money into Free.
We TRIED to be cheapo at OG and found we sucked there.
Trying to get by with scrubs at OG and Safety have been our biggest issue the past 5 years.
You need NFL caliber players everywhere.
Starting rookie undrafted free agents at Safety is a good way to get yourselves murdered.
Starting DL have real value but they are also largely rotational players.
You can get by with less that superstars there is you have legit depth.
It doesn't work that way for coverage.
Carr isn't coming out for a few plays to rest.