Well, I call it a 100-day-challenge for a reason. Have to play the game to get it done. I am on day 46 now. The final DLC pack released in late February while March and April are/were completely devoid of interesting Wii U and 3DS retail releases, so it was a good time to start the challenge. It's 100 days because there is an achievement for amiibo gifts and I can get only one per day.

The game throws tutorials for everything at you, so you probably weren't paying attention when they were forced on you. The icons show for which characters the rewards are, so you usually have to play as the shown character to earn these rewards. The Link figure is the easiest to recognize because there was an actual 8-bit game that used such a sprite. By "the sad blue face" you probably mean Impa and have mistaken her pony tail for a tear; maybe you need glasses? A question mark under a reward means that you have yet to unlock that character; Ruto, Agitha, Ghirahim and Zant are unlockable on the adventure map. In any case, rewards being restricted to certain characters means that you'll have to play quite a few missions at least twice; the same goes for missions that feature two skulltullas because it's impossible to make both show up on one and the same run. Oh, and rewards that are displayed in the left golden box require an A-rank, the middle brown box shows rewards you'll get for completing the mission with any rank, and the right box shows rewards that have to be found during the mission; in adventure mode, such heart pieces and containers are always located inside fortresses, so you'll just have to conquer them until treasure chests pop up.

I'd say doing 100% on a no-DLC version of the game is more demanding than with DLC. No access to the best grinding map for EXP, no access to the best maps for grinding materials, plus the limited amount of play options would make everything much more tiresome to max out.

But actually, since there have been several free updates, 100% isn't possible without DLC anyway. Whether you've bought DLC or not, DLC-specific achievements will be in your list.

Although I suppose you only meant the completion of legend and adventure mode when you said 100%.

The rupee glitch still works and I don't think they'll ever patch it out. Conventional methods to gain rupees aren't particularly great. You could help online-Links with doable levels (so below or at your own level), because there is a high completion bonus (up to 50,000) as opposed to normal missions which only net a few thousand rupees. Having a Rupee+ skill on your weapons helps a bit too.

But grinding EXP instead of rupees is probably faster. I've mentioned the best methods without DLC in the grinding section of the FAQ.

Honestly though, most characters are ready to earn all of their rewards and A-ranks with a level in the range of 40-50. The money you earn by completing legends mode on the lower three difficulty settings and by playing the adventure map is in the millions, so you should actually be able to spend a million here or there on characters that need a boost of 15-20 levels. Get a troublesome character up to around level 40 by playing the final level of legends mode on easy, then buy another 20 levels. There are very few missions where a level above 60 feels necessary, and all of those are of the "Kill X00 enemies" type.

True Midna is pretty good. Not only does she have a wide area attack, but it's also strong. It's quite easy to play all-out devastating while still being in full control of your surroundings. Cia is also a beast with great attacks, it's no problem at all to deplete the weak spot gauge of all kinds of enemies; she's probably the best character in the game.

Tingle is hands down the worst character. A strange arsenal of attacks that are slow and weak at the same time, and make you vulnerable.

But girl a.k.a. Agitha is a powerhouse that most people loathe because she isn't easy to play as.

Agitha can juggle most sorts of enemies effortlessly with her YYX combo. There are only a few types that run unfairly through the beetle, but you can get around that by adjusting your own movement during the constant beetle spawning. Her YYYYX combo is a strong area attack and her weak spoint smash is probably the best in the game because it covers a big area and hits hard.