I didn’t understand how to use Sets in my Beginner Days, but after using more and more of them in Builds, or just testing them in a few maps, my knowledge of which Sets work together is expanding. and I am still coming up with ideas of Set combos. not all of them work out the way I thought they would, but even a failure can lead to better ideas.
the other thing is that some Sets go well with almost any Build, and others only fit into a specific Build or specific type of Build.
for the Eternal Spike you have shared, here are some ideas.
Momentum Set: this Set gives you extra DMG based on your Move Speed Bonus. you would want some extra Move Speed on a Build when using this Pet. +40% Move Speed or higher is best. the Cap is +100%.
MP Regen: Druidic Set uses high HP & MP Regen to boost the DMG of Poison DoT DMG if you wan to make a Poison Element type of Build. Plagued Set would also be good if you went with Poison.
Dodge: Pathfinder Set uses a % of your Dodge to increase DMG & DMG Reduction. +60% Dodge or better works well with this Set.
HP & MP: a lot of HP & MP is good for PVP, but for PVE, it is good for Farm Build or beginner Characters. on higher Floors, monsters get so powerful that they can one shot kill you, so HP isn’t very necessary. an Equality Set & Equivalence Mythic Combo could make use of the HP & MP on this Spike, or a Blood Magic Mythic. a Masochism Set & Defiant Set and/or Blood Magic Mythic combo could make good use of this Spike also. the extra MP could make it easier to use the Hunger Set.
these are just some ideas, hope it helps make your Eternal Spike useful & happy!
you never know how good a Pet can be until you try it out. my Pathfinder, Momentum, & Demonic Pets get the biggest work out on my Builds, and some of the others I have some ideas for them, and a few others I want to at least make a test Build with them to see if I want to keep them or, umm, convert them to Dust or sell them.
here is a story I wrote after I used my very first Slime Pet in a few Adventures.
I hope you can take your Spike out on some cool Adventures and maybe share a story sometime.