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You may have been thrown off by a mistake in the on-line texts of Caesar. It threw me off when I tried reading this, too. The second sentence should read:
Cum id non impetrassent, petebant uti ad eos equites qui agmen antecessissent praemitteret eosque pugna prohiberet, . . .
To confirm this I looked at the 1987 Teubner edition (edited by W. Hering). In addition to supplying the missing -que, he doesn’t bracket equites, meaning that he thinks it should not be deleted, contrary to the on-line texts. There’s no textual note at the bottom of the page that indicating that some of the manuscripts on which the printed text is based do not read -que, which means that the omission of -que in the on-line texts is just a pure and simple error. The 1900 Oxford edition of du Pontet is the same as the Teubner text: eosque, and equites isn’t bracketed.
This passage is difficult because much of it is in indirect discourse after actual or implied main verbs in secondary tenses (imperfect or perfect), so that subordinate clauses are imperfect, perfect or pluperfect subjunctive, according to the standard rules for sequence of tenses.
The main verbs introducing indirect discourse are orabant, petebant, ostendebant, arbitrabatur, etc. There are verbs depending on these that are subjunctive because they are indirect commands or requests: ne longius progrederetur orabant, petebant uti . . . praemitteret eosque . . . prohiberet
quae a Caesare ferretur – subjunctive because it is a relative clause in indirect discourse, part of what was said.
qui nuntiarent – subjunctive because it’s a relative clause of purpose.
What specifically was the word that threw you off?
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condicionem ferre means “offer terms”. This is the first idiom given in Lewis & Short under condicio:
http://perseus.uchicago.edu/cgi-bin/philologic/getobject.pl?c.2:4080.lewisandshort
Cassell’s is ok for getting a rough idea of what a word means, but you need to turn to Lewis & Short when you want an in-depth review of the whole range of meanings that a particular word can express. L&S has a wealth of examples and identifies specific authors and periods. You can use the on-line version, but if you go on in Latin, you will want a copy of your own at some point, despite the cost. You can get a good used copy on-line for less than $100, and a photographic reprint for much less (but the quality of the photographic reprints tends to be spotty). The Oxford Latin Dictionary is even better, but it’s much more expensive and less easy to use on account of its size.
potestatem facere – “give them the power or authority”
frequens – now you have a common meaning, “in great numbers.”
http://perseus.uchicago.edu/cgi-bin/philologic/getobject.pl?c.5:1306.lewisandshort
Again, use Lewis & Short when you’re having trouble with a passage.
Don’t worry about your progress. Every Latin text has difficulties that trip up even experienced readers. Not everything in Caesar is “easy/intermediate level.”
The main reason why Caesar is assigned (or used to be assigned) to students after they’ve gone through the basic grammar is that his prose, although very plain and unadorned, exhibits all of the complex constructions which the student just learned–purpose clauses, result clauses, conditionals, etc., and, above all, indirect discourse that incorporates the other complex syntactic constructions–in the context of real Latin prose. Caesar isn’t necessarily easy, but he’s good for assimilating the grammar in the context of real Latin written by an acknowledged master of Latin prose.
Good luck with your reading!
Thanks for the help and advice!
I looked on Amazon and used copies of Lewis & Short start from around $80 (for an “acceptable” – the prices shoot up from there, with the second-cheapest being $120). I’ll have to get that for or after Christmas because funds are short right now (my job isn’t the best, to be charitable); given the price I may have to wait a bit for one to be offered for double-digits. I’d need the book: I can’t work off a computer monitor. Just an idiosyncrasy of mine, which seems to be shared by many.
The fourth result on Amazon for “lewis short” is “Two Men Are Better Than One: A Sexy Threesome Bisexual Short Story” for the Kindle. Not sure if it’s against forum decorum to mention that but it gave me a chuckle.
You should also try ABEBooks, which is owned by Amazon but may have more listings. Make sure the condition is good. In the meantime, use the on-line version. You may even find that the on-line version answers your needs.
Don’t be anxious about your reading ability. It comes with time. Learning a foreign language isn’t easy.
Yeah it’s definitely a good idea to cover the Engish translation with a notecard, this helped me a look as it restricts the temptation to peak 
However, looking over to check your understanding from time to time is also good to make sure you are 100% with it.
ABEbooks is also a great suggestion, so be sure to try that out