Here's some stats from my testnet node:
~/.bitcoin/testnet3# du -sh *
4.0K banlist.dat
4.0K bitcoind.pid
27G blocks
1.3G chainstate
1.5M database
4.0K db.log
562M debug.log
244K fee_estimates.dat
36K mempool.dat
2.7M peers.dat
2.5M wallet.dat
1.4M wasabi_wallet.dat
~/.bitcoin/testnet3/blocks# find ./ -type f -name 'blk*.dat' -exec du -ch {} + | grep total$
24G total
~/.bitcoin/testnet3/blocks# find ./ -type f -name 'rev*.dat' -exec du -ch {} + | grep total$
2.8G total
/.bitcoin/testnet3/blocks/index# du -sh .
333M .
As for OP's question:
- electrum can be run on testnet
- wasabi can be run on testnet
- bitcoin core can be run on testnet
- a local copy of coinb.in can be run on testnet
- armory can be run on testnet
- btcd can be run on testnet
- knots can be run on testnet
- a local copy of bitaddress.org can be run on testnet
Take your pick
I guess the wallet you pick depends on the tutorial you want to give... Electrum is SPV and has a lot of coin controll options, wasabi has that built in privacy (including a coinjoin gui), core has even more features than electrum and it's a full node, coinb.in has an easy gui to learn the basics of tx creation, armory is built on top of bitcoind, btcd and knots have a little bit different feature set, bitaddress.org teaches about the many representation ways of keys,...