Yep! Thanks for tag.
@Emperor Spriggan and I are reading through the manga together for fun since series ended.... analyzing everything from ships to battles to plot. And we are about to do phantom lord right now.
As for the ships we are looking at it based on 1) author's intent (was Mashima really aiming at a shipping or close bond), 2) fan's interpretation (could a person interpret an interaction as potentially romantic), 3) anime influence (did the anime make something more romantic then manga), 4) consistency/logic of relationship. As for Natsu ships
@Emperor Spriggan ships Naza and I ship Nalu. Neither of us ships Nali.
And right now we are both at conclusion that there are no ships prior to phantom Lord from Mashima himself. All interactions within Erza and Lucy and Natsu were platonic.
But someone could interpret certain moments in Daybreak, Eisenwall, Galuna as "Shippy" but they could also be more sibling bond with Naza (Erza punching him in the stomach then letting him rest in her lap) and platonic with Nalu (breaking into her house) Gray on the other hand seems a bit more of a "ladies" man early on. Him looking at Virgo's panties, flirting with Lucy, calling Erza cute on Galuna. But even this can be described as harmless humor from Mashima. The only one that seemed to have romantic influence was Jellal x Ultear with their flirting but even then he laughed at her getting smacked around by Natsu.
Also the anime made certain moments seem more romantic like Lucy pulling Natsu back from hurting himself in Eisenwall. We just did the chapter yesterday where Erza wants to take a bath with Gray and Natsu from phantom Lord and really that's "friendzoning/sibling zoning" to the max. I dare any non gay male to take a bath with Erza and not get a hard on.
With that being said, I personally believe (from reading the manga multiple times) that phantom Lord was the arc where Mashima started teasing ships but it was more for teasing - Grayza hug, Lucy jumping to Natsu, Natsu catching Lucy getting the same "boner face" in chapter 50 as Stone Age omake, even Gray taking care of Erza, Gruvia's fight/Juvia being in love with Gray, Natsu/Lisanna omake, and Natsu grabbing Erza falling in battle, Lucy blushing at Natsu literally the whole damn arc.
And it's right after Phantom Lord you had an implosion of ships - Lolu in Loke arc and Fighting Festival, Gajevy in fighting festival, about 6 omakes dedicated to Nalu, you had Jerza, Grayza, Naza and Simza in ToH, then Minor Nalu and Naza in FF but Jerza, Naza, Nalu, NaWen(?) in OS, Nali in Edolas, Edolas Nalu and Earthland Nalu plus Lucy Ashley x Earthland Natsu in Edolas, introduction of Everelf in Tenrou.
Edolas/tenrou cemented these ships because really, none of the main ships have changed since then, but you do see a decline in other ships - Lolu, Nali, Naza, Graylu, Grayza - after Tenrou.
But also canonly you could see it from - Gray seeing Juvia in a new light, Gajeel growing closer to levy, Natsu and Lucy becoming inseparable.
People make fun of drunk Erza calling out the ships in the Christmas omake but I personally have to question if this was something she really felt watching Juvia always being around Gray, Natsu and Lucy always together, Levy leave team shadowgear to be more with Gajeel. Mira and Evergreen interacting more with Laxus and Elfman. Cuz who was there for Erza.... and the easy answer is Jellal. Which is why I always feel their ship is the most tragic and mature. Not because of how Mashima executed it poorly at times but because of "Jerza want to be together and can't."