Looks pretty young for a 'mature' bonsai holly.
Not sure that the problem is too many low branches but the lowest branch is definitely way too thick compared to the main trunk. And way too straight and long and taller than the main trunk.
You have lots of choices. Most will reduce the tree to very little in order to promote growth where it would look better.
1. Chop the main trunk immediately above that first branch, change planting angle to make that current branch into the main trunk. It will also need further chops to reduce the length of that branch. This adds taper and bends to the trunk.
2. Chop first and second branches quite short to force new shoots much closer to the trunk then develop the new shoots as ramification for those branches. Brings ramification on the branches closer to trunk line and defines a more tree shaped bonsai.
3. Remove first branch and main trunk just above 2nd branch, change planting angle to make that 2nd branch the main trunk. That branch will also need reduction to add further taper, bends and ramification to the future trunk line. Adds taper and bend to the trunk line.
There's probably lots more possibilities but I can't see any real quick possibilities from these 2 pics.