The best way is to recharge and buy them. Or gather 20k CPs and wait for good event to get them. While gathering 20k CPs get as many frags for free as you can. And ofc you pick one ninja and go for him,

Both minato and sasuke cost around 20-24k ingots/CPs. As a f2p you will need around 3 months to get that amount.. In those 3 months you can get a lot of frags for free and save quite a lot of CPs that way.

The Madara you are asking for cost 3000$. easy to get :)

I wasn't aware of characters being elite, either way...

There are different means to getting different characters.

Recruit-Has some basic ones, good ones, and great ones. Who there is varies on what treasure you're pulling from. Seal doesn't have much to offer, but ones like 5 Kage and Great Ninja War both have some pretty good ones, though some people consider 5 kage's people outdated. (I still think they're worth grabbing, but there are other ways to get the guys. Unless we're talking the super-rares (yellow outline), then it's just a big invest, usually)

In game shops-There are a few of these, Group Shop, Black Market, Groceries store (If you really consider that a way.), and, most notably, the ninja collect scrolls in the Ninja area. Black market and Group shop are a slower way of piecing together people, nobody that big, the biggest would probably be the Kazekage Gaara frag that pops up here and there. Group shop has a few handy ones. Groceries store's not worth going over, and the collect scrolls lets you get a decent amount of people, including a few rares from treasures, who can be pretty handy. (Danzo and Killer Bee are two good ones. Hanzo's not bad either, but he's a little pricey.).

Various other in game methods-Elite instances, frag refinement, rewards for power, rewards for finishing chapters, that sort of thing.

And, the most notable method, events. Each week, every Thursday, the event cycle changes. This stuff can be found in hot topics. This is the main way of getting bigger people in this day and age. Edo Minato, Rinnegan Sasuke, Supah Sagetoes (Or 6 paths), they're all in these events. As for Decadara/10 tails Madara, well... as Aca1902 mentioned earlier, he's only a good 3000 dollars once his rebate comes in every 3 months... I think. He's only been here last December and last March, so if it is 3 months and you reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaally want the guy, and have the money to spare, then you'd have to put in 3k once his event rolls by, which may be next month. Good luck with getting the guy otherwise. On a side note, each of the metagame people, like Supah Sagetoes, Rinnesasuke, AoG Konan, Edo Hokages 2-4 (1's a different story.), all of those guys, plus a few others who I won't mention, are about 16k ingots/coupons on average each. They may be a little lower or higher, but... 16k's a good estimate for most of them, give or take Supah Sagetoes.

Also, I don't know who you'd consider elite, but do keep in mind that them being fancy or major doesn't make them top of the line. Some people may look super cool, but may end up lackluster. Also, what do you consider elite?