At low percents, I generally try to land grabs or FP setups, since things don't really start linking freely until the opponent starts tumbling from hits. If you're opponent is consistent enough, you could always try DA>fsmash>DT or DA>ftilt>"so on". Both seem to cover the DI down-away well enough, and a dsmash out of ftilt may actually be safer than a tipped fsmash.
At percentages in which your opponent will tumble, you can technically link DA>ASC repeatedly as long as they are within reach (within reach read: "they aren't knocked to high"), and should you be of the bold kind, end that string on a DTC>utilt (aiming for a cross-up) to either turn the combo around using >ASC>fair or end the string with a usmash.