Welcome to Loopers-Delight. This is a great forum to ask questions. Many many people here are available to help.
A few things come to mind after reading your posting.
A lot of looping people are on a Quest for a Better Device to suit there needs and budget. There are a lot of looping units out there today. Don't feel bashful about selling what you first get and moving on. Rather than sticking with something you don't like. This is obvious, I know. But I mention it so as to take some pressure off the first unit you buy -- it need not be so precious a choice.
1) Will you want to store loops which you would want to recall and play along with afterwards - or do you only need to create things live?
2) How long do you guess (in seconds) are the phrases you might like to loop?
3) Do you hope to have sections (A/B/A/C) to your loops - or just a steady background overwhich you might add a layer or two?
Don't think you need to have definitive answers to these questions, but the answers you have will point you towards different tools.
1) If you want to recall previous loops that are stored, that is a feature some devices provide - and some do not.
2) If you think the phrases you may want to loop are short - then older devices (which can be found used) may OK. Newer devices tend to have longer available looping time (as technology has advanced quite quickly).
3) If you require the ability to subtract layers also, then that knocks out quite a few devices.
I'm sure others here will have a few more suggestions.
Here is a link worth investigating: http://www.loopers-delight.com/tools/tools.html
By the way, I believe Zoe Keating uses an Electrix Repeater.
Best of luck.