I have a weapons questions.
How do I get powerful once?
Lana – Midna – Child Link and a few more have dreadful ones…
And it takes time to up levels on characters.
I still haven’t finished any maps!
More powerful weapon tiers are rewards on the standard adventure map (for the 13 characters in the left and middle column of the finalized roster) and the Master Quest map (Cia, Volga, Wizzro). Once you've unlocked these higher tiers of weapons, they get added to the mix of randomized weapon drops, so from then on it's a matter of luck. Replaying the mission that unlocks a specific weapon and clearing it with an A-rank guarantees you such a weapon, so it is possible to reduce the luck factor considerably and making it only a matter of amount of stars and skill slots for the weapon you desire. Twilight Midna, Tingle and Young Link are exceptions as all of their weapon tiers are unlocked as soon as you get these characters; Link's Epona and spinner, and Zelda's staff also have all of their tiers unlocked right off the bat, so for all of the aforementioned exceptions the only thing you can do is to play the game persistently and hope for the best.
As for leveling up, I'll copy-paste from the original post. It doesn't take much effort to get a character to level 30 and the requirements to do so are very low.
10. I am in dire need of a higher level to clear a certain map. How do I level up efficiently?
For the early game, play the final level of legends mode on easy (even doable with tier 1 weapons), equip a weapon with Experience+ and buy an Experience+ potion for 50 bronze materials and 10,000 rupees. One run should take around 15 minutes and net five or more level ups as long as you are below level 30. You shouldn't bother with this strategy anymore once you are past level 40. At that point most of the missions on the first adventure map can be cleared with relative ease; if not, simply buy EXP with rupees in the training room because your problem is probably a character you don't like to play as anyway.
If you don't have any DLC, the extra map in adventure mode is the best source for experience, although its missions aren't all that great for fast grinding. It's merely a last resort if you don't have any other options, meaning no purchased DLC and buying EXP with rupees doesn't work because that is only possible up to the level of your best character's level.
If you have bought DLC and already earned the tier 3 weapon for the character you want to level up, make your way to the bottom left square of the Master Quest adventure map, play with all possible Experience+ stuff and use magic efficiently to earn even more EXP. One run takes ten minutes, so including loading and result screens, you can do five runs per hour. During that timespan you can easily raise a character from level 40 to 80 which will not only prepare that character for the Twilight Princess adventure map, but also make pretty much everything easy on the first two adventure maps. The Master Quest map doesn't really require higher levels than 50. This level grinding can and should be combined with the unlocking of the 25,000 skills because you can rack up 2,000+ kills per run.