Zair and PK Fire are your primary zoning tools. Don't whif Usmash. PK Freeze has deceptively little endlag and can pressure your opponent offstage. Zair and Dtilt have a variety of things they combo into, so learn and practice those percentages.
Speaking of combos, Dthrow is your bread and butter, and has one of if not the best throw rewards in the game. Practice everything it has to offer, just about every combo video or tutorial goes into Dthrow. Fair puts the opponent in tumble around 60% and opens up a jablock > KO opportunity, as does Zair somewhere around 100%.
A tether grab is an arduous transition from non-tethers, so be mindful of its endlag and range. Fortunately your reward's worth the risk; D-throw can combo at almost any realistic percent, B-throw kills at the ledge, and U-throw is a reliable kill around 140%. I wouldn't recommend F-throw.
Psi Magnet, Zair, and F-smash net you a plethora of favorable matchups against projectile users moreso than Ness since Magnet and Zair have hitboxes (Zair eats most projectiles and has ridiculous range). Wavebounce PK Fire is a great spacing tool when wavebounced, giving Lucas a decent poke option. Nair is a good combo string that eats most characters with high airdodge frame rate for breakfast, apparently. Dair trips. Bair is arguably your go-to spike when edgeguarding.
Your tether and extended PK2 recovery gives you a much higher chance to recover than Ness. You can also go under FD with Tether > release > PK Fire > PKT2. Not entirely sure about that one, but there's a video of it somewhere.
For matchups, I can't say for sure about others, but you should wreck Ganon and Toon Link. Lucas can combo Ganon for days, and our neutral can cancel anything Tink throws at us on paper. In application, it's important to know that Tink loses to shield. Like, badly. He has no grab reward, and his tether makes that an easily exploitable weakness. Abuse it vigorously, and while Toon Link can combo into his bombs in a variety of ways including kill setups, grabbing the bomb ourselves gives us a variety of options as well, including bomb > footstool > jablock.
