DS/DSi consoles are alive and active more than ever, it's just that their users are always there playing with them, and they don't have the time, nor the desire, to answer you.
Luckily for you there is always yours truly who, despite his many commitments, is always ready to lend a hand to those in need.
That said, I can recommend a r4 Gold Pro, used by many users, whose kernel is r4i-sdhc but you can also use YSMenu. However, its own kernel allows a limited number of roms and only in the SD root. YSMenu is more compatible, easy to use and effective, but incompatible with some games (e.g. Inazuma series). This flashcart is very cheap, and from this year without "time bomb" (however easily circumvented).
Even better, and also cheap, the 482 in 1 DS card. It's an Ace3ds+ that uses the Wood kernel; it already contains a microSD with games, but you can delete duplicates or games that don't interest you and put others. Or use another microSD of higher quality, but be sure to use the same, identical kernel. I've never found a game that didn't work with it!
I own both flashcarts.
The choice is yours.
P.S. Peeking on your profile I noticed that you are american, so I don't know if there, these cards are easily available or as cheap as in Europe.