Was farming FGs with Limitless, and then I found myself like this:
Leaving aside the fact that I won, I noticed, among other games I had against Lionheart, that a single Quintessence could kill him there (assuming he would have used anubis' effect on the last pharaoh). Playing two would, leaving them both being the last cards in your deck, be a killer.
Said so, a budget deck for lionheart would be:
6 Dimensional Shield
2-4 Quintessence
20-22 Aether Pillar
Aether Mark
If you have an Essential Halfblood Farmer you should already have this, pretty much, quints and few pillars aside.
Playing more Quints would increase your likelyhood of not losing because of them being on bottom deck, while playing less increases your likelyhood of having more pillars in the starting hand. Since the number of pillars is already big enough, you can easily play 4 Quints and 20 Pillars.
If you have upped sundials you can play them too, or even change the mark to Time to power them, increasing the number of turns you can stop your opponent's attacks.
6 Dim Shields are 18 turns of no attacks and no weapon damage,
6 Sundials are 6 turns of no attacks.
Together they make 24 Turns. Considering he has 80 cards in deck with double drawing and 10 Hourglasses, extimating he can play one every 2,5 turns, he'll draw at a crazy speed where probably the 18 turns of Dim Shields are enough. Said this, sundials power up your deck, but not necessarily needed, play them only if you have them upped and it's ok.