Recognizing that you have a very limited budget, I recommend considering the depth keys. There have been many posts about using depth keys. Some people hate the idea and just say to bite the bullet and invest in a code cutter. But, others use depth keys regularly. Once you have them made or purchased, use is cheap. You only have to get the sets you need as you need them. I personally have access to an ITL code cutter, a Framon, and an HPC Blitz. However I still carry and use depth keys for about 20 different brands. I have created some non-standard, special step, keys for specific customers on the ITL and made depth keys to match. With depth keys, you only need one machine and will not have to change cutter wheel and guide. Use of depth keys is definitely slower and will be a pain in the neck if you have a big masterkey job to do. If so, either get a code cutter or sub-contract code cutting of at least the file copy of all of your new change keys.
The answer to your question about double angle cutters (and guide) depends on your profiency and how often you need to create keys. A standard duplication cutter has one straight side. The guide is always an exact match in regard to shape. When using depth keys this straight side produces no ramp to allow the pins to ride up on some of the key cuts. A double angle cutter produces the ramp on both sides at the same time and is faster. My favorite solution is to make a "ramp file". Using a square or triangular file, grind and polish smooth one corner along the full length of the file. This corner can then be put into the cut with a straight ramp and you can file the angle. Because the corner is smooth it will not change the depth of the cut. This works great to smooth off the sharp points of new keys that are rough going in and out of the lock.
Other uses of depth keys are: as a key gauge, without having to use a micrometer. You can compare them to cut keys or gauge the pins directly in a lock for the code. If impressioning, duplicate a '0' or '1' on a blank and you have your perfect spacing. Some people cut to the next depth on the space where a mark shows and do not use a file.
Just a few thoughts on depth keys. You make the choice.
Nothing is foolproof to a talented fool. Wisdom is not just in determining how to do something, but also includes determining whether it should be done at all.