I can add to this something.
First of all, keep in mind, that converting 10 N WC to 1 R WC also costs you some Pero (1000 if i recall it right). So it is not 10 000 Pero for N WC = 1 R WC.
Secondly - when there is no Event active, you can buy N Gacha Tickets for 1000 Pero each, instead of 1500 Pero during Events. That means N gacha and N Wildcards are equal in price, but buying N Gacha results in all the benefits mentioned above, so it is much more Pero-effective, than buying N WC and converting them into R WC.
Plus, if you want to get an extra SR WC every day and you consider yourself a plodding person, you'll need do as i do - to spend all of your pero on N Gacha Tickets, (and, mostly, it will never be enough of N gacha Tickets anyway, so you'll HAVE to buy some even during the Events) then, enlist for the "Get 3 N Girl Cards" daily mission, then, after getting these using N Gacha, enlist for "Get 2 R Girl Cards" daily mission, quickly get them in R Gacha - if you want to minimize the use of N Gacha Tickets and time for getting them in the N gacha (that will require 2 additional R Gacha Tickets, but you can always get one by completing another Daily Mission, that requires you to get first 3, then 5 and then 10 Chance TIme rolls in the Exploration Mode, or Elite Guard Search, and get enough of them during Events) and then enlist for doing "Get 1 SR Girl Card" Daily Mission, and roll the N Gacha until you'll finally get one - you'll need to roll N Gacha for about 50-70 times for that (sometimes - much less, like 10-30. 100-120 is the worst case scenario you'll ever get).
I also can recommend you to not level-up at all those of your cards (especially - the N cards, and in case of R and SR cards - not to level them up over lvl 50 or so) that you can get in the N Gacha. Why? Because, getting them in the N Gacha will result in a permanent level-up of those cards, which means 1k Pero in case of N card, 11k Pero in case of R card and 120k in case if you'll get an SR card when you'll use that N Gacha ticket or get it during Chance Time on any other Search Gacha. If you'll max out said cards to lvl 100, and get them for rolling any Search Gacha or the Girl Hunt Quest Gacha later, you'll just get 300 Pero if you'll get an N card and 700 Pero if you'll get R card and 1500 Pero if you'll get an SR card that way. So you can count, how much Pero you'll lose if you'll max out your cards too quick using Wild Cards.
So, i recommend you to use WildCards only on those cards that you can't get on any Gacha that consumes Stamina (that means, the unique cards that you'll get as Ranking or EP rewards during Events, from Facebook campaigns and so on.

Btw, i'd like to ask those who know - what will i get if i'll get a card that i've already maxed out in the E-gacha, SR Guaranteed Gacha, Revival Gacha and else? Corresponding WildCards? And are those SR1 WIld Cards even in those Gachas, or are they giving at least SR3 or SR5 or EX Wild Cards for those (since their tickets are extremely valueable)