Using some homebrew i created. How to design a level 1 encounter with 7 level 1 characters

Me and my friends decided to play some dnd 5th edition. The issue is, though i am a long term DM i am only well-versed in the rules for 3.5e and Pathfinder 1st, same as Open Legend but it uses a completely different base system than the other ones.

I am essentially playing in a world that has been changed by the invention of Magitek. Technically it was discovered by some ancient ruins by the big empires expedition into the wilderness, though they honed and reverse engineered all that old tech in those ruins.

Right now my adventuring party is about to meet in the common tavern setting. All of those characters are of level 1 and consist of:

-Life Cleric

-Artificer

-Barbarian

-Monk

-The UA Pheonix Sorcerer with a few tweaks.

-A warlock with homebrew. Pact of the Vengeful Spirit as a mounted warlock kind of deal.

-Blood Hunter

Right now i want to make a small adventure playing in a neutral swiss like country, which is outside of the large and political conflicts of this world. To get the characters to bond in a more neutral environment. Since 1 Character comes from the "evil" empire and the other 3 come from it’s natural enemy. So to build up a group i decided to let them start in a neutral environment. Though i would like to introduce that little homebrew i entered into the world.

Magitek Items or rather Items with the Magitek Keyword are like magical items, but require fuel to sustain themselves for a more beneficial effect. What i was thinking of was that a Beast Tribe with enough Intelligence, probably Goblinoids, stole some shipments from the place they are currently situated at and are using that to raid the lands.

Though personally with a relatively balanced lineup of characters and essentially 7 turns in player character action economy. I personally do not know how to make an engaging encounter for them or multiple during this mini-adventure so that the players feel challenged and feel that this is an actual threat if these items get out of control. Obviously i would also not hand my players magitek items early on in the campaign. The Life Cleric is a Kleptomaniac. So should i maybe build in a failsafe ?

I’d require some good help for encounter building against overwhelming action economy in 5e as in 3.5 or pathfinder 1st i can handle it. Though there i feel it is quite confusing. Any advice is helpful here.

Thanks for the help in advance.